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x y : ℂ
⊢ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by | simp [(by norm_num : (2 : ℂ) ≠ 0)] | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x y : ℂ
⊢ 2 ≠ 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by | norm_num | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x y : ℂ
⊢ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 ↔ (∃ k, y = 2 * ↑k * ↑π + x) ∨ ∃ k, y = 2 * ↑k * ↑π - x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
| apply or_congr | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h₁
x y : ℂ
⊢ sin ((x - y) / 2) = 0 ↔ ∃ k, y = 2 * ↑k * ↑π + x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
| field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)] | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x y : ℂ
⊢ -2 ≠ 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by | norm_num | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h₂
x y : ℂ
⊢ sin ((x + y) / 2) = 0 ↔ ∃ k, y = 2 * ↑k * ↑π - x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
| field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)] | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x y : ℂ
⊢ -2 ≠ 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by | norm_num | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h₁
x y : ℂ
⊢ (∃ k, x = ↑k * ↑π * 2 + y) ↔ ∃ k, y = ↑k * ↑π * 2 + x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
| constructor | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h₁.mp
x y : ℂ
⊢ (∃ k, x = ↑k * ↑π * 2 + y) → ∃ k, y = ↑k * ↑π * 2 + x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · | rintro ⟨k, rfl⟩ | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h₁.mp.intro
y : ℂ
k : ℤ
⊢ ∃ k_1, y = ↑k_1 * ↑π * 2 + (↑k * ↑π * 2 + y) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; | use -k | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h
y : ℂ
k : ℤ
⊢ y = ↑(-k) * ↑π * 2 + (↑k * ↑π * 2 + y) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; | simp | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h₁.mpr
x y : ℂ
⊢ (∃ k, y = ↑k * ↑π * 2 + x) → ∃ k, x = ↑k * ↑π * 2 + y | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · | rintro ⟨k, rfl⟩ | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h₁.mpr.intro
x : ℂ
k : ℤ
⊢ ∃ k_1, x = ↑k_1 * ↑π * 2 + (↑k * ↑π * 2 + x) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; | use -k | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h
x : ℂ
k : ℤ
⊢ x = ↑(-k) * ↑π * 2 + (↑k * ↑π * 2 + x) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; | simp | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.80_0.wRglntQQQHH0e1R | theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x y : ℂ
⊢ sin x = sin y ↔ ∃ k, y = 2 * ↑k * ↑π + x ∨ y = (2 * ↑k + 1) * ↑π - x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
| simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add] | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.94_0.wRglntQQQHH0e1R | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x y : ℂ
⊢ (∃ k, y = 2 * ↑k * ↑π + (x - ↑π / 2) + ↑π / 2 ∨ y = 2 * ↑k * ↑π - (x - ↑π / 2) + ↑π / 2) ↔
∃ k, y = 2 * ↑k * ↑π + x ∨ y = (2 * ↑k + 1) * ↑π - x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
| refine' exists_congr fun k => or_congr _ _ | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.94_0.wRglntQQQHH0e1R | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case refine'_1
x y : ℂ
k : ℤ
⊢ y = 2 * ↑k * ↑π + (x - ↑π / 2) + ↑π / 2 ↔ y = 2 * ↑k * ↑π + x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> | refine' Eq.congr rfl _ | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.94_0.wRglntQQQHH0e1R | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case refine'_2
x y : ℂ
k : ℤ
⊢ y = 2 * ↑k * ↑π - (x - ↑π / 2) + ↑π / 2 ↔ y = (2 * ↑k + 1) * ↑π - x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> | refine' Eq.congr rfl _ | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.94_0.wRglntQQQHH0e1R | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case refine'_1
x y : ℂ
k : ℤ
⊢ 2 * ↑k * ↑π + (x - ↑π / 2) + ↑π / 2 = 2 * ↑k * ↑π + x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> | field_simp | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.94_0.wRglntQQQHH0e1R | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case refine'_2
x y : ℂ
k : ℤ
⊢ 2 * ↑k * ↑π - (x - ↑π / 2) + ↑π / 2 = (2 * ↑k + 1) * ↑π - x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> | field_simp | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.94_0.wRglntQQQHH0e1R | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case refine'_1
x y : ℂ
k : ℤ
⊢ 2 * ↑k * ↑π * 2 + (x * 2 - ↑π) + ↑π = (2 * ↑k * ↑π + x) * 2 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> | ring | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.94_0.wRglntQQQHH0e1R | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case refine'_2
x y : ℂ
k : ℤ
⊢ 2 * ↑k * ↑π * 2 - (x * 2 - ↑π) + ↑π = ((2 * ↑k + 1) * ↑π - x) * 2 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> | ring | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.94_0.wRglntQQQHH0e1R | theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x y : ℂ
h :
((∀ (k : ℤ), x ≠ (2 * ↑k + 1) * ↑π / 2) ∧ ∀ (l : ℤ), y ≠ (2 * ↑l + 1) * ↑π / 2) ∨
(∃ k, x = (2 * ↑k + 1) * ↑π / 2) ∧ ∃ l, y = (2 * ↑l + 1) * ↑π / 2
⊢ tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
| rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩) | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.100_0.wRglntQQQHH0e1R | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case inl.intro
x y : ℂ
h1 : ∀ (k : ℤ), x ≠ (2 * ↑k + 1) * ↑π / 2
h2 : ∀ (l : ℤ), y ≠ (2 * ↑l + 1) * ↑π / 2
⊢ tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· | rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div] | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.100_0.wRglntQQQHH0e1R | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case inl.intro
x y : ℂ
h1 : ∀ (k : ℤ), x ≠ (2 * ↑k + 1) * ↑π / 2
h2 : ∀ (l : ℤ), y ≠ (2 * ↑l + 1) * ↑π / 2
⊢ (sin x * cos y / (cos x * cos y) + cos x * sin y / (cos x * cos y)) /
(cos x * cos y / (cos x * cos y) - sin x * sin y / (cos x * cos y)) =
(tan x + tan y) / (1 - tan x * tan y) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
| simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)] | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.100_0.wRglntQQQHH0e1R | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case inr.intro.intro.intro
k l : ℤ
⊢ tan ((2 * ↑k + 1) * ↑π / 2 + (2 * ↑l + 1) * ↑π / 2) =
(tan ((2 * ↑k + 1) * ↑π / 2) + tan ((2 * ↑l + 1) * ↑π / 2)) /
(1 - tan ((2 * ↑k + 1) * ↑π / 2) * tan ((2 * ↑l + 1) * ↑π / 2)) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· | haveI t := tan_int_mul_pi_div_two | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.100_0.wRglntQQQHH0e1R | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case inr.intro.intro.intro
k l : ℤ
t : ∀ (n : ℤ), tan (↑n * ↑π / 2) = 0
⊢ tan ((2 * ↑k + 1) * ↑π / 2 + (2 * ↑l + 1) * ↑π / 2) =
(tan ((2 * ↑k + 1) * ↑π / 2) + tan ((2 * ↑l + 1) * ↑π / 2)) /
(1 - tan ((2 * ↑k + 1) * ↑π / 2) * tan ((2 * ↑l + 1) * ↑π / 2)) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
| obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1)) | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.100_0.wRglntQQQHH0e1R | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case inr.intro.intro.intro
k l : ℤ
t : ∀ (n : ℤ), tan (↑n * ↑π / 2) = 0
hx : tan (↑(2 * k + 1) * ↑π / 2) = 0
hy : tan (↑(2 * l + 1) * ↑π / 2) = 0
hxy : tan (↑(2 * k + 1 + (2 * l + 1)) * ↑π / 2) = 0
⊢ tan ((2 * ↑k + 1) * ↑π / 2 + (2 * ↑l + 1) * ↑π / 2) =
(tan ((2 * ↑k + 1) * ↑π / 2) + tan ((2 * ↑l + 1) * ↑π / 2)) /
(1 - tan ((2 * ↑k + 1) * ↑π / 2) * tan ((2 * ↑l + 1) * ↑π / 2)) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
| simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.100_0.wRglntQQQHH0e1R | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case inr.intro.intro.intro
k l : ℤ
t : ∀ (n : ℤ), tan (↑n * ↑π / 2) = 0
hx : tan ((2 * ↑k + 1) * ↑π / 2) = 0
hy : tan ((2 * ↑l + 1) * ↑π / 2) = 0
hxy : tan ((2 * ↑k + 1 + (2 * ↑l + 1)) * ↑π / 2) = 0
⊢ tan ((2 * ↑k + 1) * ↑π / 2 + (2 * ↑l + 1) * ↑π / 2) =
(tan ((2 * ↑k + 1) * ↑π / 2) + tan ((2 * ↑l + 1) * ↑π / 2)) /
(1 - tan ((2 * ↑k + 1) * ↑π / 2) * tan ((2 * ↑l + 1) * ↑π / 2)) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
| rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy] | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.100_0.wRglntQQQHH0e1R | theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
z : ℂ
⊢ tan (2 * z) = 2 * tan z / (1 - tan z ^ 2) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
| by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2 | theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.124_0.wRglntQQQHH0e1R | theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case pos
z : ℂ
h : ∀ (k : ℤ), z ≠ (2 * ↑k + 1) * ↑π / 2
⊢ tan (2 * z) = 2 * tan z / (1 - tan z ^ 2) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· | rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)] | theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.124_0.wRglntQQQHH0e1R | theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case neg
z : ℂ
h : ¬∀ (k : ℤ), z ≠ (2 * ↑k + 1) * ↑π / 2
⊢ tan (2 * z) = 2 * tan z / (1 - tan z ^ 2) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· | rw [not_forall_not] at h | theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.124_0.wRglntQQQHH0e1R | theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case neg
z : ℂ
h : ∃ x, z = (2 * ↑x + 1) * ↑π / 2
⊢ tan (2 * z) = 2 * tan z / (1 - tan z ^ 2) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
| rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)] | theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.124_0.wRglntQQQHH0e1R | theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x y : ℂ
h :
((∀ (k : ℤ), x ≠ (2 * ↑k + 1) * ↑π / 2) ∧ ∀ (l : ℤ), y * I ≠ (2 * ↑l + 1) * ↑π / 2) ∨
(∃ k, x = (2 * ↑k + 1) * ↑π / 2) ∧ ∃ l, y * I = (2 * ↑l + 1) * ↑π / 2
⊢ tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
| rw [tan_add h, tan_mul_I, mul_assoc] | theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.131_0.wRglntQQQHH0e1R | theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
z : ℂ
h :
((∀ (k : ℤ), ↑z.re ≠ (2 * ↑k + 1) * ↑π / 2) ∧ ∀ (l : ℤ), ↑z.im * I ≠ (2 * ↑l + 1) * ↑π / 2) ∨
(∃ k, ↑z.re = (2 * ↑k + 1) * ↑π / 2) ∧ ∃ l, ↑z.im * I = (2 * ↑l + 1) * ↑π / 2
⊢ tan z = (tan ↑z.re + tanh ↑z.im * I) / (1 - tan ↑z.re * tanh ↑z.im * I) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
| convert tan_add_mul_I h | theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.140_0.wRglntQQQHH0e1R | theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h.e'_2.h.e'_1
z : ℂ
h :
((∀ (k : ℤ), ↑z.re ≠ (2 * ↑k + 1) * ↑π / 2) ∧ ∀ (l : ℤ), ↑z.im * I ≠ (2 * ↑l + 1) * ↑π / 2) ∨
(∃ k, ↑z.re = (2 * ↑k + 1) * ↑π / 2) ∧ ∃ l, ↑z.im * I = (2 * ↑l + 1) * ↑π / 2
⊢ z = ↑z.re + ↑z.im * I | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; | exact (re_add_im z).symm | theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.140_0.wRglntQQQHH0e1R | theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
z w : ℂ
⊢ cos z = w ↔ cexp (z * I) ^ 2 - 2 * w * cexp (z * I) + 1 = 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
| rw [← sub_eq_zero] | theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.161_0.wRglntQQQHH0e1R | theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
z w : ℂ
⊢ cos z - w = 0 ↔ cexp (z * I) ^ 2 - 2 * w * cexp (z * I) + 1 = 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
| field_simp [cos, exp_neg, exp_ne_zero] | theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.161_0.wRglntQQQHH0e1R | theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
z w : ℂ
⊢ cexp (z * I) * cexp (z * I) + 1 - cexp (z * I) * 2 * w = 0 ↔ cexp (z * I) ^ 2 - 2 * w * cexp (z * I) + 1 = 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
| refine' Eq.congr _ rfl | theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.161_0.wRglntQQQHH0e1R | theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
z w : ℂ
⊢ cexp (z * I) * cexp (z * I) + 1 - cexp (z * I) * 2 * w = cexp (z * I) ^ 2 - 2 * w * cexp (z * I) + 1 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
| ring | theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.161_0.wRglntQQQHH0e1R | theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
⊢ Function.Surjective cos | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
| intro x | theorem cos_surjective : Function.Surjective cos := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℂ
⊢ ∃ a, cos a = x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
| obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw | theorem cos_surjective : Function.Surjective cos := by
intro x
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℂ
⊢ ∃ w, ∃ (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
| rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩ | theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case intro
x w : ℂ
hw : 1 * w * w + ?m.61281 * w + ?m.61282 = 0
⊢ ∃ w, ∃ (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
| refine' ⟨w, _, hw⟩ | theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case intro
x w : ℂ
hw : 1 * w * w + -2 * x * w + 1 = 0
⊢ w ≠ 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
| rintro rfl | theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case intro
x : ℂ
hw : 1 * 0 * 0 + -2 * x * 0 + 1 = 0
⊢ False | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
| simp only [zero_add, one_ne_zero, mul_zero] at hw | theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case intro.intro
x w : ℂ
w₀ : w ≠ 0
hw : 1 * w * w + -2 * x * w + 1 = 0
⊢ ∃ a, cos a = x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
| refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩ | theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case intro.intro
x w : ℂ
w₀ : w ≠ 0
hw : 1 * w * w + -2 * x * w + 1 = 0
⊢ cexp (log w / I * I) ^ 2 - 2 * x * cexp (log w / I * I) + 1 = 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
| rw [div_mul_cancel _ I_ne_zero, exp_log w₀] | theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case intro.intro
x w : ℂ
w₀ : w ≠ 0
hw : 1 * w * w + -2 * x * w + 1 = 0
⊢ w ^ 2 - 2 * x * w + 1 = 0 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
| convert hw using 1 | theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case h.e'_2
x w : ℂ
w₀ : w ≠ 0
hw : 1 * w * w + -2 * x * w + 1 = 0
⊢ w ^ 2 - 2 * x * w + 1 = 1 * w * w + -2 * x * w + 1 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
| ring | theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.169_0.wRglntQQQHH0e1R | theorem cos_surjective : Function.Surjective cos | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
⊢ Function.Surjective sin | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
| intro x | theorem sin_surjective : Function.Surjective sin := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.189_0.wRglntQQQHH0e1R | theorem sin_surjective : Function.Surjective sin | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℂ
⊢ ∃ a, sin a = x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
| rcases cos_surjective x with ⟨z, rfl⟩ | theorem sin_surjective : Function.Surjective sin := by
intro x
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.189_0.wRglntQQQHH0e1R | theorem sin_surjective : Function.Surjective sin | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
case intro
z : ℂ
⊢ ∃ a, sin a = cos z | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
| exact ⟨z + π / 2, sin_add_pi_div_two z⟩ | theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.189_0.wRglntQQQHH0e1R | theorem sin_surjective : Function.Surjective sin | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
θ : ℝ
⊢ cos θ ≠ 0 ↔ ∀ (k : ℤ), θ ≠ (2 * ↑k + 1) * π / 2 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
exact ⟨z + π / 2, sin_add_pi_div_two z⟩
#align complex.sin_surjective Complex.sin_surjective
@[simp]
theorem range_sin : Set.range sin = Set.univ :=
sin_surjective.range_eq
#align complex.range_sin Complex.range_sin
end Complex
namespace Real
open scoped Real
theorem cos_eq_zero_iff {θ : ℝ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 :=
mod_cast @Complex.cos_eq_zero_iff θ
#align real.cos_eq_zero_iff Real.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
| rw [← not_exists, not_iff_not, cos_eq_zero_iff] | theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.210_0.wRglntQQQHH0e1R | theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℝ
hx : 0 < x
hx' : x < 1
⊢ x < sin (π / 2 * x) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
exact ⟨z + π / 2, sin_add_pi_div_two z⟩
#align complex.sin_surjective Complex.sin_surjective
@[simp]
theorem range_sin : Set.range sin = Set.univ :=
sin_surjective.range_eq
#align complex.range_sin Complex.range_sin
end Complex
namespace Real
open scoped Real
theorem cos_eq_zero_iff {θ : ℝ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 :=
mod_cast @Complex.cos_eq_zero_iff θ
#align real.cos_eq_zero_iff Real.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align real.cos_ne_zero_iff Real.cos_ne_zero_iff
theorem cos_eq_cos_iff {x y : ℝ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
mod_cast @Complex.cos_eq_cos_iff x y
#align real.cos_eq_cos_iff Real.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℝ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x :=
mod_cast @Complex.sin_eq_sin_iff x y
#align real.sin_eq_sin_iff Real.sin_eq_sin_iff
theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) := by
| simpa [mul_comm x] using
strictConcaveOn_sin_Icc.2 ⟨le_rfl, pi_pos.le⟩ ⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩
pi_div_two_pos.ne (sub_pos.2 hx') hx | theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.223_0.wRglntQQQHH0e1R | theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℝ
hx : 0 ≤ x
hx' : x ≤ 1
⊢ x ≤ sin (π / 2 * x) | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
exact ⟨z + π / 2, sin_add_pi_div_two z⟩
#align complex.sin_surjective Complex.sin_surjective
@[simp]
theorem range_sin : Set.range sin = Set.univ :=
sin_surjective.range_eq
#align complex.range_sin Complex.range_sin
end Complex
namespace Real
open scoped Real
theorem cos_eq_zero_iff {θ : ℝ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 :=
mod_cast @Complex.cos_eq_zero_iff θ
#align real.cos_eq_zero_iff Real.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align real.cos_ne_zero_iff Real.cos_ne_zero_iff
theorem cos_eq_cos_iff {x y : ℝ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
mod_cast @Complex.cos_eq_cos_iff x y
#align real.cos_eq_cos_iff Real.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℝ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x :=
mod_cast @Complex.sin_eq_sin_iff x y
#align real.sin_eq_sin_iff Real.sin_eq_sin_iff
theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.2 ⟨le_rfl, pi_pos.le⟩ ⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩
pi_div_two_pos.ne (sub_pos.2 hx') hx
#align real.lt_sin_mul Real.lt_sin_mul
theorem le_sin_mul {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ 1) : x ≤ sin (π / 2 * x) := by
| simpa [mul_comm x] using
strictConcaveOn_sin_Icc.concaveOn.2 ⟨le_rfl, pi_pos.le⟩
⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩ (sub_nonneg.2 hx') hx | theorem le_sin_mul {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ 1) : x ≤ sin (π / 2 * x) := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.229_0.wRglntQQQHH0e1R | theorem le_sin_mul {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ 1) : x ≤ sin (π / 2 * x) | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℝ
hx : 0 < x
hx' : x < π / 2
⊢ 2 / π * x < sin x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
exact ⟨z + π / 2, sin_add_pi_div_two z⟩
#align complex.sin_surjective Complex.sin_surjective
@[simp]
theorem range_sin : Set.range sin = Set.univ :=
sin_surjective.range_eq
#align complex.range_sin Complex.range_sin
end Complex
namespace Real
open scoped Real
theorem cos_eq_zero_iff {θ : ℝ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 :=
mod_cast @Complex.cos_eq_zero_iff θ
#align real.cos_eq_zero_iff Real.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align real.cos_ne_zero_iff Real.cos_ne_zero_iff
theorem cos_eq_cos_iff {x y : ℝ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
mod_cast @Complex.cos_eq_cos_iff x y
#align real.cos_eq_cos_iff Real.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℝ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x :=
mod_cast @Complex.sin_eq_sin_iff x y
#align real.sin_eq_sin_iff Real.sin_eq_sin_iff
theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.2 ⟨le_rfl, pi_pos.le⟩ ⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩
pi_div_two_pos.ne (sub_pos.2 hx') hx
#align real.lt_sin_mul Real.lt_sin_mul
theorem le_sin_mul {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ 1) : x ≤ sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.concaveOn.2 ⟨le_rfl, pi_pos.le⟩
⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩ (sub_nonneg.2 hx') hx
#align real.le_sin_mul Real.le_sin_mul
theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x := by
| rw [← inv_div] | theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.235_0.wRglntQQQHH0e1R | theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℝ
hx : 0 < x
hx' : x < π / 2
⊢ (π / 2)⁻¹ * x < sin x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
exact ⟨z + π / 2, sin_add_pi_div_two z⟩
#align complex.sin_surjective Complex.sin_surjective
@[simp]
theorem range_sin : Set.range sin = Set.univ :=
sin_surjective.range_eq
#align complex.range_sin Complex.range_sin
end Complex
namespace Real
open scoped Real
theorem cos_eq_zero_iff {θ : ℝ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 :=
mod_cast @Complex.cos_eq_zero_iff θ
#align real.cos_eq_zero_iff Real.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align real.cos_ne_zero_iff Real.cos_ne_zero_iff
theorem cos_eq_cos_iff {x y : ℝ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
mod_cast @Complex.cos_eq_cos_iff x y
#align real.cos_eq_cos_iff Real.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℝ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x :=
mod_cast @Complex.sin_eq_sin_iff x y
#align real.sin_eq_sin_iff Real.sin_eq_sin_iff
theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.2 ⟨le_rfl, pi_pos.le⟩ ⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩
pi_div_two_pos.ne (sub_pos.2 hx') hx
#align real.lt_sin_mul Real.lt_sin_mul
theorem le_sin_mul {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ 1) : x ≤ sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.concaveOn.2 ⟨le_rfl, pi_pos.le⟩
⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩ (sub_nonneg.2 hx') hx
#align real.le_sin_mul Real.le_sin_mul
theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x := by
rw [← inv_div]
| simpa [-inv_div, mul_inv_cancel_left₀ pi_div_two_pos.ne'] using @lt_sin_mul ((π / 2)⁻¹ * x)
(mul_pos (inv_pos.2 pi_div_two_pos) hx) (by rwa [← div_eq_inv_mul, div_lt_one pi_div_two_pos]) | theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x := by
rw [← inv_div]
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.235_0.wRglntQQQHH0e1R | theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℝ
hx : 0 < x
hx' : x < π / 2
⊢ (π / 2)⁻¹ * x < 1 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
exact ⟨z + π / 2, sin_add_pi_div_two z⟩
#align complex.sin_surjective Complex.sin_surjective
@[simp]
theorem range_sin : Set.range sin = Set.univ :=
sin_surjective.range_eq
#align complex.range_sin Complex.range_sin
end Complex
namespace Real
open scoped Real
theorem cos_eq_zero_iff {θ : ℝ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 :=
mod_cast @Complex.cos_eq_zero_iff θ
#align real.cos_eq_zero_iff Real.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align real.cos_ne_zero_iff Real.cos_ne_zero_iff
theorem cos_eq_cos_iff {x y : ℝ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
mod_cast @Complex.cos_eq_cos_iff x y
#align real.cos_eq_cos_iff Real.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℝ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x :=
mod_cast @Complex.sin_eq_sin_iff x y
#align real.sin_eq_sin_iff Real.sin_eq_sin_iff
theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.2 ⟨le_rfl, pi_pos.le⟩ ⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩
pi_div_two_pos.ne (sub_pos.2 hx') hx
#align real.lt_sin_mul Real.lt_sin_mul
theorem le_sin_mul {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ 1) : x ≤ sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.concaveOn.2 ⟨le_rfl, pi_pos.le⟩
⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩ (sub_nonneg.2 hx') hx
#align real.le_sin_mul Real.le_sin_mul
theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x := by
rw [← inv_div]
simpa [-inv_div, mul_inv_cancel_left₀ pi_div_two_pos.ne'] using @lt_sin_mul ((π / 2)⁻¹ * x)
(mul_pos (inv_pos.2 pi_div_two_pos) hx) (by | rwa [← div_eq_inv_mul, div_lt_one pi_div_two_pos] | theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x := by
rw [← inv_div]
simpa [-inv_div, mul_inv_cancel_left₀ pi_div_two_pos.ne'] using @lt_sin_mul ((π / 2)⁻¹ * x)
(mul_pos (inv_pos.2 pi_div_two_pos) hx) (by | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.235_0.wRglntQQQHH0e1R | theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℝ
hx : 0 ≤ x
hx' : x ≤ π / 2
⊢ 2 / π * x ≤ sin x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
exact ⟨z + π / 2, sin_add_pi_div_two z⟩
#align complex.sin_surjective Complex.sin_surjective
@[simp]
theorem range_sin : Set.range sin = Set.univ :=
sin_surjective.range_eq
#align complex.range_sin Complex.range_sin
end Complex
namespace Real
open scoped Real
theorem cos_eq_zero_iff {θ : ℝ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 :=
mod_cast @Complex.cos_eq_zero_iff θ
#align real.cos_eq_zero_iff Real.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align real.cos_ne_zero_iff Real.cos_ne_zero_iff
theorem cos_eq_cos_iff {x y : ℝ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
mod_cast @Complex.cos_eq_cos_iff x y
#align real.cos_eq_cos_iff Real.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℝ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x :=
mod_cast @Complex.sin_eq_sin_iff x y
#align real.sin_eq_sin_iff Real.sin_eq_sin_iff
theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.2 ⟨le_rfl, pi_pos.le⟩ ⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩
pi_div_two_pos.ne (sub_pos.2 hx') hx
#align real.lt_sin_mul Real.lt_sin_mul
theorem le_sin_mul {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ 1) : x ≤ sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.concaveOn.2 ⟨le_rfl, pi_pos.le⟩
⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩ (sub_nonneg.2 hx') hx
#align real.le_sin_mul Real.le_sin_mul
theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x := by
rw [← inv_div]
simpa [-inv_div, mul_inv_cancel_left₀ pi_div_two_pos.ne'] using @lt_sin_mul ((π / 2)⁻¹ * x)
(mul_pos (inv_pos.2 pi_div_two_pos) hx) (by rwa [← div_eq_inv_mul, div_lt_one pi_div_two_pos])
#align real.mul_lt_sin Real.mul_lt_sin
/-- In the range `[0, π / 2]`, we have a linear lower bound on `sin`. This inequality forms one half
of Jordan's inequality, the other half is `Real.sin_lt` -/
theorem mul_le_sin {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ π / 2) : 2 / π * x ≤ sin x := by
| rw [← inv_div] | /-- In the range `[0, π / 2]`, we have a linear lower bound on `sin`. This inequality forms one half
of Jordan's inequality, the other half is `Real.sin_lt` -/
theorem mul_le_sin {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ π / 2) : 2 / π * x ≤ sin x := by
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.241_0.wRglntQQQHH0e1R | /-- In the range `[0, π / 2]`, we have a linear lower bound on `sin`. This inequality forms one half
of Jordan's inequality, the other half is `Real.sin_lt` -/
theorem mul_le_sin {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ π / 2) : 2 / π * x ≤ sin x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℝ
hx : 0 ≤ x
hx' : x ≤ π / 2
⊢ (π / 2)⁻¹ * x ≤ sin x | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
exact ⟨z + π / 2, sin_add_pi_div_two z⟩
#align complex.sin_surjective Complex.sin_surjective
@[simp]
theorem range_sin : Set.range sin = Set.univ :=
sin_surjective.range_eq
#align complex.range_sin Complex.range_sin
end Complex
namespace Real
open scoped Real
theorem cos_eq_zero_iff {θ : ℝ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 :=
mod_cast @Complex.cos_eq_zero_iff θ
#align real.cos_eq_zero_iff Real.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align real.cos_ne_zero_iff Real.cos_ne_zero_iff
theorem cos_eq_cos_iff {x y : ℝ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
mod_cast @Complex.cos_eq_cos_iff x y
#align real.cos_eq_cos_iff Real.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℝ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x :=
mod_cast @Complex.sin_eq_sin_iff x y
#align real.sin_eq_sin_iff Real.sin_eq_sin_iff
theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.2 ⟨le_rfl, pi_pos.le⟩ ⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩
pi_div_two_pos.ne (sub_pos.2 hx') hx
#align real.lt_sin_mul Real.lt_sin_mul
theorem le_sin_mul {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ 1) : x ≤ sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.concaveOn.2 ⟨le_rfl, pi_pos.le⟩
⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩ (sub_nonneg.2 hx') hx
#align real.le_sin_mul Real.le_sin_mul
theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x := by
rw [← inv_div]
simpa [-inv_div, mul_inv_cancel_left₀ pi_div_two_pos.ne'] using @lt_sin_mul ((π / 2)⁻¹ * x)
(mul_pos (inv_pos.2 pi_div_two_pos) hx) (by rwa [← div_eq_inv_mul, div_lt_one pi_div_two_pos])
#align real.mul_lt_sin Real.mul_lt_sin
/-- In the range `[0, π / 2]`, we have a linear lower bound on `sin`. This inequality forms one half
of Jordan's inequality, the other half is `Real.sin_lt` -/
theorem mul_le_sin {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ π / 2) : 2 / π * x ≤ sin x := by
rw [← inv_div]
| simpa [-inv_div, mul_inv_cancel_left₀ pi_div_two_pos.ne'] using @le_sin_mul ((π / 2)⁻¹ * x)
(mul_nonneg (inv_nonneg.2 pi_div_two_pos.le) hx)
(by rwa [← div_eq_inv_mul, div_le_one pi_div_two_pos]) | /-- In the range `[0, π / 2]`, we have a linear lower bound on `sin`. This inequality forms one half
of Jordan's inequality, the other half is `Real.sin_lt` -/
theorem mul_le_sin {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ π / 2) : 2 / π * x ≤ sin x := by
rw [← inv_div]
| Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.241_0.wRglntQQQHH0e1R | /-- In the range `[0, π / 2]`, we have a linear lower bound on `sin`. This inequality forms one half
of Jordan's inequality, the other half is `Real.sin_lt` -/
theorem mul_le_sin {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ π / 2) : 2 / π * x ≤ sin x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
x : ℝ
hx : 0 ≤ x
hx' : x ≤ π / 2
⊢ (π / 2)⁻¹ * x ≤ 1 | /-
Copyright (c) 2018 Chris Hughes. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Chris Hughes, Abhimanyu Pallavi Sudhir, Jean Lo, Calle Sönne, Benjamin Davidson
-/
import Mathlib.Algebra.QuadraticDiscriminant
import Mathlib.Analysis.Convex.SpecificFunctions.Deriv
#align_import analysis.special_functions.trigonometric.complex from "leanprover-community/mathlib"@"8f9fea08977f7e450770933ee6abb20733b47c92"
/-!
# Complex trigonometric functions
Basic facts and derivatives for the complex trigonometric functions.
Several facts about the real trigonometric functions have the proofs deferred here, rather than
`Analysis.SpecialFunctions.Trigonometric.Basic`,
as they are most easily proved by appealing to the corresponding fact for complex trigonometric
functions, or require additional imports which are not available in that file.
-/
noncomputable section
namespace Complex
open Set Filter
open scoped Real
theorem cos_eq_zero_iff {θ : ℂ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 := by
have h : (exp (θ * I) + exp (-θ * I)) / 2 = 0 ↔ exp (2 * θ * I) = -1 := by
rw [@div_eq_iff _ _ (exp (θ * I) + exp (-θ * I)) 2 0 two_ne_zero, zero_mul,
add_eq_zero_iff_eq_neg, neg_eq_neg_one_mul, ← div_eq_iff (exp_ne_zero _), ← exp_sub]
congr 3; ring_nf
rw [cos, h, ← exp_pi_mul_I, exp_eq_exp_iff_exists_int, mul_right_comm]
refine' exists_congr fun x => _
refine' (iff_of_eq <| congr_arg _ _).trans (mul_right_inj' <| mul_ne_zero two_ne_zero I_ne_zero)
field_simp; ring
#align complex.cos_eq_zero_iff Complex.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℂ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align complex.cos_ne_zero_iff Complex.cos_ne_zero_iff
theorem sin_eq_zero_iff {θ : ℂ} : sin θ = 0 ↔ ∃ k : ℤ, θ = k * π := by
rw [← Complex.cos_sub_pi_div_two, cos_eq_zero_iff]
constructor
· rintro ⟨k, hk⟩
use k + 1
field_simp [eq_add_of_sub_eq hk]
ring
· rintro ⟨k, rfl⟩
use k - 1
field_simp
ring
#align complex.sin_eq_zero_iff Complex.sin_eq_zero_iff
theorem sin_ne_zero_iff {θ : ℂ} : sin θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π := by
rw [← not_exists, not_iff_not, sin_eq_zero_iff]
#align complex.sin_ne_zero_iff Complex.sin_ne_zero_iff
theorem tan_eq_zero_iff {θ : ℂ} : tan θ = 0 ↔ ∃ k : ℤ, θ = k * π / 2 := by
have h := (sin_two_mul θ).symm
rw [mul_assoc] at h
rw [tan, div_eq_zero_iff, ← mul_eq_zero, ← zero_mul (1 / 2 : ℂ), mul_one_div,
CancelDenoms.cancel_factors_eq_div h two_ne_zero, mul_comm]
simpa only [zero_div, zero_mul, Ne.def, not_false_iff, field_simps] using
sin_eq_zero_iff
#align complex.tan_eq_zero_iff Complex.tan_eq_zero_iff
theorem tan_ne_zero_iff {θ : ℂ} : tan θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ k * π / 2 := by
rw [← not_exists, not_iff_not, tan_eq_zero_iff]
#align complex.tan_ne_zero_iff Complex.tan_ne_zero_iff
theorem tan_int_mul_pi_div_two (n : ℤ) : tan (n * π / 2) = 0 :=
tan_eq_zero_iff.mpr (by use n)
#align complex.tan_int_mul_pi_div_two Complex.tan_int_mul_pi_div_two
theorem cos_eq_cos_iff {x y : ℂ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
calc
cos x = cos y ↔ cos x - cos y = 0 := sub_eq_zero.symm
_ ↔ -2 * sin ((x + y) / 2) * sin ((x - y) / 2) = 0 := by rw [cos_sub_cos]
_ ↔ sin ((x + y) / 2) = 0 ∨ sin ((x - y) / 2) = 0 := by simp [(by norm_num : (2 : ℂ) ≠ 0)]
_ ↔ sin ((x - y) / 2) = 0 ∨ sin ((x + y) / 2) = 0 := or_comm
_ ↔ (∃ k : ℤ, y = 2 * k * π + x) ∨ ∃ k : ℤ, y = 2 * k * π - x := by
apply or_congr <;>
field_simp [sin_eq_zero_iff, (by norm_num : -(2 : ℂ) ≠ 0), eq_sub_iff_add_eq',
sub_eq_iff_eq_add, mul_comm (2 : ℂ), mul_right_comm _ (2 : ℂ)]
constructor <;> · rintro ⟨k, rfl⟩; use -k; simp
_ ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x := exists_or.symm
#align complex.cos_eq_cos_iff Complex.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℂ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x := by
simp only [← Complex.cos_sub_pi_div_two, cos_eq_cos_iff, sub_eq_iff_eq_add]
refine' exists_congr fun k => or_congr _ _ <;> refine' Eq.congr rfl _ <;> field_simp <;> ring
#align complex.sin_eq_sin_iff Complex.sin_eq_sin_iff
theorem tan_add {x y : ℂ}
(h : ((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y = (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) := by
rcases h with (⟨h1, h2⟩ | ⟨⟨k, rfl⟩, ⟨l, rfl⟩⟩)
· rw [tan, sin_add, cos_add, ←
div_div_div_cancel_right (sin x * cos y + cos x * sin y)
(mul_ne_zero (cos_ne_zero_iff.mpr h1) (cos_ne_zero_iff.mpr h2)),
add_div, sub_div]
simp only [← div_mul_div_comm, tan, mul_one, one_mul, div_self (cos_ne_zero_iff.mpr h1),
div_self (cos_ne_zero_iff.mpr h2)]
· haveI t := tan_int_mul_pi_div_two
obtain ⟨hx, hy, hxy⟩ := t (2 * k + 1), t (2 * l + 1), t (2 * k + 1 + (2 * l + 1))
simp only [Int.cast_add, Int.cast_two, Int.cast_mul, Int.cast_one, hx, hy] at hx hy hxy
rw [hx, hy, add_zero, zero_div, mul_div_assoc, mul_div_assoc, ←
add_mul (2 * (k : ℂ) + 1) (2 * l + 1) (π / 2), ← mul_div_assoc, hxy]
#align complex.tan_add Complex.tan_add
theorem tan_add' {x y : ℂ}
(h : (∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y ≠ (2 * l + 1) * π / 2) :
tan (x + y) = (tan x + tan y) / (1 - tan x * tan y) :=
tan_add (Or.inl h)
#align complex.tan_add' Complex.tan_add'
theorem tan_two_mul {z : ℂ} : tan (2 * z) = (2 : ℂ) * tan z / ((1 : ℂ) - tan z ^ 2) := by
by_cases h : ∀ k : ℤ, z ≠ (2 * k + 1) * π / 2
· rw [two_mul, two_mul, sq, tan_add (Or.inl ⟨h, h⟩)]
· rw [not_forall_not] at h
rw [two_mul, two_mul, sq, tan_add (Or.inr ⟨h, h⟩)]
#align complex.tan_two_mul Complex.tan_two_mul
theorem tan_add_mul_I {x y : ℂ}
(h :
((∀ k : ℤ, x ≠ (2 * k + 1) * π / 2) ∧ ∀ l : ℤ, y * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, x = (2 * k + 1) * π / 2) ∧ ∃ l : ℤ, y * I = (2 * l + 1) * π / 2) :
tan (x + y * I) = (tan x + tanh y * I) / (1 - tan x * tanh y * I) := by
rw [tan_add h, tan_mul_I, mul_assoc]
set_option linter.uppercaseLean3 false in
#align complex.tan_add_mul_I Complex.tan_add_mul_I
theorem tan_eq {z : ℂ}
(h :
((∀ k : ℤ, (z.re : ℂ) ≠ (2 * k + 1) * π / 2) ∧
∀ l : ℤ, (z.im : ℂ) * I ≠ (2 * l + 1) * π / 2) ∨
(∃ k : ℤ, (z.re : ℂ) = (2 * k + 1) * π / 2) ∧
∃ l : ℤ, (z.im : ℂ) * I = (2 * l + 1) * π / 2) :
tan z = (tan z.re + tanh z.im * I) / (1 - tan z.re * tanh z.im * I) := by
convert tan_add_mul_I h; exact (re_add_im z).symm
#align complex.tan_eq Complex.tan_eq
open scoped Topology
theorem continuousOn_tan : ContinuousOn tan {x | cos x ≠ 0} :=
continuousOn_sin.div continuousOn_cos fun _x => id
#align complex.continuous_on_tan Complex.continuousOn_tan
@[continuity]
theorem continuous_tan : Continuous fun x : {x | cos x ≠ 0} => tan x :=
continuousOn_iff_continuous_restrict.1 continuousOn_tan
#align complex.continuous_tan Complex.continuous_tan
theorem cos_eq_iff_quadratic {z w : ℂ} :
cos z = w ↔ exp (z * I) ^ 2 - 2 * w * exp (z * I) + 1 = 0 := by
rw [← sub_eq_zero]
field_simp [cos, exp_neg, exp_ne_zero]
refine' Eq.congr _ rfl
ring
#align complex.cos_eq_iff_quadratic Complex.cos_eq_iff_quadratic
theorem cos_surjective : Function.Surjective cos := by
intro x
obtain ⟨w, w₀, hw⟩ : ∃ (w : _) (_ : w ≠ 0), 1 * w * w + -2 * x * w + 1 = 0 := by
rcases exists_quadratic_eq_zero one_ne_zero
⟨_, (cpow_nat_inv_pow _ two_ne_zero).symm.trans <| pow_two _⟩ with
⟨w, hw⟩
refine' ⟨w, _, hw⟩
rintro rfl
simp only [zero_add, one_ne_zero, mul_zero] at hw
refine' ⟨log w / I, cos_eq_iff_quadratic.2 _⟩
rw [div_mul_cancel _ I_ne_zero, exp_log w₀]
convert hw using 1
ring
#align complex.cos_surjective Complex.cos_surjective
@[simp]
theorem range_cos : Set.range cos = Set.univ :=
cos_surjective.range_eq
#align complex.range_cos Complex.range_cos
theorem sin_surjective : Function.Surjective sin := by
intro x
rcases cos_surjective x with ⟨z, rfl⟩
exact ⟨z + π / 2, sin_add_pi_div_two z⟩
#align complex.sin_surjective Complex.sin_surjective
@[simp]
theorem range_sin : Set.range sin = Set.univ :=
sin_surjective.range_eq
#align complex.range_sin Complex.range_sin
end Complex
namespace Real
open scoped Real
theorem cos_eq_zero_iff {θ : ℝ} : cos θ = 0 ↔ ∃ k : ℤ, θ = (2 * k + 1) * π / 2 :=
mod_cast @Complex.cos_eq_zero_iff θ
#align real.cos_eq_zero_iff Real.cos_eq_zero_iff
theorem cos_ne_zero_iff {θ : ℝ} : cos θ ≠ 0 ↔ ∀ k : ℤ, θ ≠ (2 * k + 1) * π / 2 := by
rw [← not_exists, not_iff_not, cos_eq_zero_iff]
#align real.cos_ne_zero_iff Real.cos_ne_zero_iff
theorem cos_eq_cos_iff {x y : ℝ} : cos x = cos y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = 2 * k * π - x :=
mod_cast @Complex.cos_eq_cos_iff x y
#align real.cos_eq_cos_iff Real.cos_eq_cos_iff
theorem sin_eq_sin_iff {x y : ℝ} :
sin x = sin y ↔ ∃ k : ℤ, y = 2 * k * π + x ∨ y = (2 * k + 1) * π - x :=
mod_cast @Complex.sin_eq_sin_iff x y
#align real.sin_eq_sin_iff Real.sin_eq_sin_iff
theorem lt_sin_mul {x : ℝ} (hx : 0 < x) (hx' : x < 1) : x < sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.2 ⟨le_rfl, pi_pos.le⟩ ⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩
pi_div_two_pos.ne (sub_pos.2 hx') hx
#align real.lt_sin_mul Real.lt_sin_mul
theorem le_sin_mul {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ 1) : x ≤ sin (π / 2 * x) := by
simpa [mul_comm x] using
strictConcaveOn_sin_Icc.concaveOn.2 ⟨le_rfl, pi_pos.le⟩
⟨pi_div_two_pos.le, half_le_self pi_pos.le⟩ (sub_nonneg.2 hx') hx
#align real.le_sin_mul Real.le_sin_mul
theorem mul_lt_sin {x : ℝ} (hx : 0 < x) (hx' : x < π / 2) : 2 / π * x < sin x := by
rw [← inv_div]
simpa [-inv_div, mul_inv_cancel_left₀ pi_div_two_pos.ne'] using @lt_sin_mul ((π / 2)⁻¹ * x)
(mul_pos (inv_pos.2 pi_div_two_pos) hx) (by rwa [← div_eq_inv_mul, div_lt_one pi_div_two_pos])
#align real.mul_lt_sin Real.mul_lt_sin
/-- In the range `[0, π / 2]`, we have a linear lower bound on `sin`. This inequality forms one half
of Jordan's inequality, the other half is `Real.sin_lt` -/
theorem mul_le_sin {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ π / 2) : 2 / π * x ≤ sin x := by
rw [← inv_div]
simpa [-inv_div, mul_inv_cancel_left₀ pi_div_two_pos.ne'] using @le_sin_mul ((π / 2)⁻¹ * x)
(mul_nonneg (inv_nonneg.2 pi_div_two_pos.le) hx)
(by | rwa [← div_eq_inv_mul, div_le_one pi_div_two_pos] | /-- In the range `[0, π / 2]`, we have a linear lower bound on `sin`. This inequality forms one half
of Jordan's inequality, the other half is `Real.sin_lt` -/
theorem mul_le_sin {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ π / 2) : 2 / π * x ≤ sin x := by
rw [← inv_div]
simpa [-inv_div, mul_inv_cancel_left₀ pi_div_two_pos.ne'] using @le_sin_mul ((π / 2)⁻¹ * x)
(mul_nonneg (inv_nonneg.2 pi_div_two_pos.le) hx)
(by | Mathlib.Analysis.SpecialFunctions.Trigonometric.Complex.241_0.wRglntQQQHH0e1R | /-- In the range `[0, π / 2]`, we have a linear lower bound on `sin`. This inequality forms one half
of Jordan's inequality, the other half is `Real.sin_lt` -/
theorem mul_le_sin {x : ℝ} (hx : 0 ≤ x) (hx' : x ≤ π / 2) : 2 / π * x ≤ sin x | Mathlib_Analysis_SpecialFunctions_Trigonometric_Complex |
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
⊢ Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
| refine' ⟨_, fun h => _⟩ | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
| Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
⊢ Independent f → LinearIndependent K (Projectivization.rep ∘ f) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· | rintro ⟨ff, hff, hh⟩ | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· | Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1.mk
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
ff : ι → V
hff : ∀ (i : ι), ff i ≠ 0
hh : LinearIndependent K ff
⊢ LinearIndependent K (Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0)) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
| choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i) | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
| Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1.mk
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
ff : ι → V
hff : ∀ (i : ι), ff i ≠ 0
hh : LinearIndependent K ff
a : ι → Kˣ
ha : ∀ (i : ι), a i • ff i = Projectivization.rep (mk K (ff i) (_ : ff i ≠ 0))
⊢ LinearIndependent K (Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0)) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
| convert hh.units_smul a | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
| Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case h.e'_4
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
ff : ι → V
hff : ∀ (i : ι), ff i ≠ 0
hh : LinearIndependent K ff
a : ι → Kˣ
ha : ∀ (i : ι), a i • ff i = Projectivization.rep (mk K (ff i) (_ : ff i ≠ 0))
⊢ (Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0)) = a • ff | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
| ext i | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
| Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case h.e'_4.h
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
ff : ι → V
hff : ∀ (i : ι), ff i ≠ 0
hh : LinearIndependent K ff
a : ι → Kˣ
ha : ∀ (i : ι), a i • ff i = Projectivization.rep (mk K (ff i) (_ : ff i ≠ 0))
i : ι
⊢ (Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0)) i = (a • ff) i | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
| exact (ha i).symm | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
| Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_2
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : LinearIndependent K (Projectivization.rep ∘ f)
⊢ Independent f | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· | convert Independent.mk _ _ h | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· | Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case h.e'_7.h
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : LinearIndependent K (Projectivization.rep ∘ f)
x✝ : ι
⊢ f x✝ = mk K ((Projectivization.rep ∘ f) x✝) (_ : ?m.15410 x✝ ≠ 0) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· | simp only [mk_rep, Function.comp_apply] | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· | Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_2
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : LinearIndependent K (Projectivization.rep ∘ f)
⊢ ∀ (i : ι), (Projectivization.rep ∘ f) i ≠ 0 | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· | intro i | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· | Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_2
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : LinearIndependent K (Projectivization.rep ∘ f)
i : ι
⊢ (Projectivization.rep ∘ f) i ≠ 0 | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
| apply rep_nonzero | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
| Mathlib.LinearAlgebra.Projectivization.Independence.46_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
⊢ Independent f ↔ CompleteLattice.Independent fun i => Projectivization.submodule (f i) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
| refine' ⟨_, fun h => _⟩ | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
| Mathlib.LinearAlgebra.Projectivization.Independence.61_0.owtLEGtk9UFDfW6 | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
⊢ Independent f → CompleteLattice.Independent fun i => Projectivization.submodule (f i) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· | rintro ⟨f, hf, hi⟩ | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· | Mathlib.LinearAlgebra.Projectivization.Independence.61_0.owtLEGtk9UFDfW6 | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1.mk
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → V
hf : ∀ (i : ι), f i ≠ 0
hi : LinearIndependent K f
⊢ CompleteLattice.Independent fun i => Projectivization.submodule ((fun i => mk K (f i) (_ : f i ≠ 0)) i) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
| simp only [submodule_mk] | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
| Mathlib.LinearAlgebra.Projectivization.Independence.61_0.owtLEGtk9UFDfW6 | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1.mk
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → V
hf : ∀ (i : ι), f i ≠ 0
hi : LinearIndependent K f
⊢ CompleteLattice.Independent fun i => Submodule.span K {f i} | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
| exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
| Mathlib.LinearAlgebra.Projectivization.Independence.61_0.owtLEGtk9UFDfW6 | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_2
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : CompleteLattice.Independent fun i => Projectivization.submodule (f i)
⊢ Independent f | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· | rw [independent_iff] | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· | Mathlib.LinearAlgebra.Projectivization.Independence.61_0.owtLEGtk9UFDfW6 | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_2
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : CompleteLattice.Independent fun i => Projectivization.submodule (f i)
⊢ LinearIndependent K (Projectivization.rep ∘ f) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
| refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _ | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
| Mathlib.LinearAlgebra.Projectivization.Independence.61_0.owtLEGtk9UFDfW6 | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_2.refine'_1
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : CompleteLattice.Independent fun i => Projectivization.submodule (f i)
i : ι
⊢ (Projectivization.rep ∘ f) i ∈ (Projectivization.submodule ∘ f) i | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· | simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _ | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· | Mathlib.LinearAlgebra.Projectivization.Independence.61_0.owtLEGtk9UFDfW6 | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_2.refine'_2
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : CompleteLattice.Independent fun i => Projectivization.submodule (f i)
i : ι
⊢ (Projectivization.rep ∘ f) i ≠ 0 | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· | exact rep_nonzero (f i) | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· | Mathlib.LinearAlgebra.Projectivization.Independence.61_0.owtLEGtk9UFDfW6 | /-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule | Mathlib_LinearAlgebra_Projectivization_Independence |
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
⊢ Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
| refine' ⟨_, fun h => _⟩ | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
| Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
⊢ Dependent f → ¬LinearIndependent K (Projectivization.rep ∘ f) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· | rintro ⟨ff, hff, hh1⟩ | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· | Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1.mk
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
ff : ι → V
hff : ∀ (i : ι), ff i ≠ 0
hh1 : ¬LinearIndependent K ff
⊢ ¬LinearIndependent K (Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0)) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
| contrapose! hh1 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
| Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1.mk
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
ff : ι → V
hff : ∀ (i : ι), ff i ≠ 0
hh1 : LinearIndependent K (Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0))
⊢ LinearIndependent K ff | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
| choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i) | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
| Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_1.mk
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
ff : ι → V
hff : ∀ (i : ι), ff i ≠ 0
hh1 : LinearIndependent K (Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0))
a : ι → Kˣ
ha : ∀ (i : ι), a i • ff i = Projectivization.rep (mk K (ff i) (_ : ff i ≠ 0))
⊢ LinearIndependent K ff | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
| convert hh1.units_smul a⁻¹ | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
| Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case h.e'_4
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
ff : ι → V
hff : ∀ (i : ι), ff i ≠ 0
hh1 : LinearIndependent K (Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0))
a : ι → Kˣ
ha : ∀ (i : ι), a i • ff i = Projectivization.rep (mk K (ff i) (_ : ff i ≠ 0))
⊢ ff = a⁻¹ • Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
| ext i | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
| Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case h.e'_4.h
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
ff : ι → V
hff : ∀ (i : ι), ff i ≠ 0
hh1 : LinearIndependent K (Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0))
a : ι → Kˣ
ha : ∀ (i : ι), a i • ff i = Projectivization.rep (mk K (ff i) (_ : ff i ≠ 0))
i : ι
⊢ ff i = (a⁻¹ • Projectivization.rep ∘ fun i => mk K (ff i) (_ : ff i ≠ 0)) i | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
| simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply] | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
| Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_2
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : ¬LinearIndependent K (Projectivization.rep ∘ f)
⊢ Dependent f | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· | convert Dependent.mk _ _ h | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· | Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case h.e'_7.h
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : ¬LinearIndependent K (Projectivization.rep ∘ f)
x✝ : ι
⊢ f x✝ = mk K ((Projectivization.rep ∘ f) x✝) (_ : ?m.37767 x✝ ≠ 0) | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· | simp only [mk_rep, Function.comp_apply] | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· | Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
case refine'_2
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
h : ¬LinearIndependent K (Projectivization.rep ∘ f)
⊢ ∀ (i : ι), (Projectivization.rep ∘ f) i ≠ 0 | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· | exact fun i => rep_nonzero (f i) | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· | Mathlib.LinearAlgebra.Projectivization.Independence.82_0.owtLEGtk9UFDfW6 | /-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) | Mathlib_LinearAlgebra_Projectivization_Independence |
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
⊢ Dependent f ↔ ¬Independent f | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· exact fun i => rep_nonzero (f i)
#align projectivization.dependent_iff Projectivization.dependent_iff
/-- Dependence is the negation of independence. -/
theorem dependent_iff_not_independent : Dependent f ↔ ¬Independent f := by
| rw [dependent_iff, independent_iff] | /-- Dependence is the negation of independence. -/
theorem dependent_iff_not_independent : Dependent f ↔ ¬Independent f := by
| Mathlib.LinearAlgebra.Projectivization.Independence.97_0.owtLEGtk9UFDfW6 | /-- Dependence is the negation of independence. -/
theorem dependent_iff_not_independent : Dependent f ↔ ¬Independent f | Mathlib_LinearAlgebra_Projectivization_Independence |
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
⊢ Independent f ↔ ¬Dependent f | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· exact fun i => rep_nonzero (f i)
#align projectivization.dependent_iff Projectivization.dependent_iff
/-- Dependence is the negation of independence. -/
theorem dependent_iff_not_independent : Dependent f ↔ ¬Independent f := by
rw [dependent_iff, independent_iff]
#align projectivization.dependent_iff_not_independent Projectivization.dependent_iff_not_independent
/-- Independence is the negation of dependence. -/
theorem independent_iff_not_dependent : Independent f ↔ ¬Dependent f := by
| rw [dependent_iff_not_independent, Classical.not_not] | /-- Independence is the negation of dependence. -/
theorem independent_iff_not_dependent : Independent f ↔ ¬Dependent f := by
| Mathlib.LinearAlgebra.Projectivization.Independence.102_0.owtLEGtk9UFDfW6 | /-- Independence is the negation of dependence. -/
theorem independent_iff_not_dependent : Independent f ↔ ¬Dependent f | Mathlib_LinearAlgebra_Projectivization_Independence |
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
u v : ℙ K V
⊢ Dependent ![u, v] ↔ u = v | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· exact fun i => rep_nonzero (f i)
#align projectivization.dependent_iff Projectivization.dependent_iff
/-- Dependence is the negation of independence. -/
theorem dependent_iff_not_independent : Dependent f ↔ ¬Independent f := by
rw [dependent_iff, independent_iff]
#align projectivization.dependent_iff_not_independent Projectivization.dependent_iff_not_independent
/-- Independence is the negation of dependence. -/
theorem independent_iff_not_dependent : Independent f ↔ ¬Dependent f := by
rw [dependent_iff_not_independent, Classical.not_not]
#align projectivization.independent_iff_not_dependent Projectivization.independent_iff_not_dependent
/-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v := by
| rw [dependent_iff_not_independent, independent_iff, linearIndependent_fin2,
Function.comp_apply, Matrix.cons_val_one, Matrix.head_cons, Ne.def] | /-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v := by
| Mathlib.LinearAlgebra.Projectivization.Independence.107_0.owtLEGtk9UFDfW6 | /-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v | Mathlib_LinearAlgebra_Projectivization_Independence |
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
u v : ℙ K V
⊢ ¬(¬Projectivization.rep v = 0 ∧ ∀ (a : K), a • Projectivization.rep v ≠ (Projectivization.rep ∘ ![u, v]) 0) ↔ u = v | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· exact fun i => rep_nonzero (f i)
#align projectivization.dependent_iff Projectivization.dependent_iff
/-- Dependence is the negation of independence. -/
theorem dependent_iff_not_independent : Dependent f ↔ ¬Independent f := by
rw [dependent_iff, independent_iff]
#align projectivization.dependent_iff_not_independent Projectivization.dependent_iff_not_independent
/-- Independence is the negation of dependence. -/
theorem independent_iff_not_dependent : Independent f ↔ ¬Dependent f := by
rw [dependent_iff_not_independent, Classical.not_not]
#align projectivization.independent_iff_not_dependent Projectivization.independent_iff_not_dependent
/-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v := by
rw [dependent_iff_not_independent, independent_iff, linearIndependent_fin2,
Function.comp_apply, Matrix.cons_val_one, Matrix.head_cons, Ne.def]
| simp only [Matrix.cons_val_zero, not_and, not_forall, Classical.not_not, Function.comp_apply,
← mk_eq_mk_iff' K _ _ (rep_nonzero u) (rep_nonzero v), mk_rep, imp_iff_right_iff] | /-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v := by
rw [dependent_iff_not_independent, independent_iff, linearIndependent_fin2,
Function.comp_apply, Matrix.cons_val_one, Matrix.head_cons, Ne.def]
| Mathlib.LinearAlgebra.Projectivization.Independence.107_0.owtLEGtk9UFDfW6 | /-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v | Mathlib_LinearAlgebra_Projectivization_Independence |
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
u v : ℙ K V
⊢ ¬Projectivization.rep v = 0 ∨ u = v | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· exact fun i => rep_nonzero (f i)
#align projectivization.dependent_iff Projectivization.dependent_iff
/-- Dependence is the negation of independence. -/
theorem dependent_iff_not_independent : Dependent f ↔ ¬Independent f := by
rw [dependent_iff, independent_iff]
#align projectivization.dependent_iff_not_independent Projectivization.dependent_iff_not_independent
/-- Independence is the negation of dependence. -/
theorem independent_iff_not_dependent : Independent f ↔ ¬Dependent f := by
rw [dependent_iff_not_independent, Classical.not_not]
#align projectivization.independent_iff_not_dependent Projectivization.independent_iff_not_dependent
/-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v := by
rw [dependent_iff_not_independent, independent_iff, linearIndependent_fin2,
Function.comp_apply, Matrix.cons_val_one, Matrix.head_cons, Ne.def]
simp only [Matrix.cons_val_zero, not_and, not_forall, Classical.not_not, Function.comp_apply,
← mk_eq_mk_iff' K _ _ (rep_nonzero u) (rep_nonzero v), mk_rep, imp_iff_right_iff]
| exact Or.inl (rep_nonzero v) | /-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v := by
rw [dependent_iff_not_independent, independent_iff, linearIndependent_fin2,
Function.comp_apply, Matrix.cons_val_one, Matrix.head_cons, Ne.def]
simp only [Matrix.cons_val_zero, not_and, not_forall, Classical.not_not, Function.comp_apply,
← mk_eq_mk_iff' K _ _ (rep_nonzero u) (rep_nonzero v), mk_rep, imp_iff_right_iff]
| Mathlib.LinearAlgebra.Projectivization.Independence.107_0.owtLEGtk9UFDfW6 | /-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v | Mathlib_LinearAlgebra_Projectivization_Independence |
ι : Type u_1
K : Type u_2
V : Type u_3
inst✝² : Field K
inst✝¹ : AddCommGroup V
inst✝ : Module K V
f : ι → ℙ K V
u v : ℙ K V
⊢ Independent ![u, v] ↔ u ≠ v | /-
Copyright (c) 2022 Michael Blyth. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Michael Blyth
-/
import Mathlib.LinearAlgebra.Projectivization.Basic
#align_import linear_algebra.projective_space.independence from "leanprover-community/mathlib"@"1e82f5ec4645f6a92bb9e02fce51e44e3bc3e1fe"
/-!
# Independence in Projective Space
In this file we define independence and dependence of families of elements in projective space.
## Implementation Details
We use an inductive definition to define the independence of points in projective
space, where the only constructor assumes an independent family of vectors from the
ambient vector space. Similarly for the definition of dependence.
## Results
- A family of elements is dependent if and only if it is not independent.
- Two elements are dependent if and only if they are equal.
# Future Work
- Define collinearity in projective space.
- Prove the axioms of a projective geometry are satisfied by the dependence relation.
- Define projective linear subspaces.
-/
open scoped LinearAlgebra.Projectivization
variable {ι K V : Type*} [Field K] [AddCommGroup V] [Module K V] {f : ι → ℙ K V}
namespace Projectivization
/-- A linearly independent family of nonzero vectors gives an independent family of points
in projective space. -/
inductive Independent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (hl : LinearIndependent K f) :
Independent fun i => mk K (f i) (hf i)
#align projectivization.independent Projectivization.Independent
/-- A family of points in a projective space is independent if and only if the representative
vectors determined by the family are linearly independent. -/
theorem independent_iff : Independent f ↔ LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh⟩
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh.units_smul a
ext i
exact (ha i).symm
· convert Independent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· intro i
apply rep_nonzero
#align projectivization.independent_iff Projectivization.independent_iff
/-- A family of points in projective space is independent if and only if the family of
submodules which the points determine is independent in the lattice-theoretic sense. -/
theorem independent_iff_completeLattice_independent :
Independent f ↔ CompleteLattice.Independent fun i => (f i).submodule := by
refine' ⟨_, fun h => _⟩
· rintro ⟨f, hf, hi⟩
simp only [submodule_mk]
exact (CompleteLattice.independent_iff_linearIndependent_of_ne_zero (R := K) hf).mpr hi
· rw [independent_iff]
refine' h.linearIndependent (Projectivization.submodule ∘ f) (fun i => _) fun i => _
· simpa only [Function.comp_apply, submodule_eq] using Submodule.mem_span_singleton_self _
· exact rep_nonzero (f i)
#align projectivization.independent_iff_complete_lattice_independent Projectivization.independent_iff_completeLattice_independent
/-- A linearly dependent family of nonzero vectors gives a dependent family of points
in projective space. -/
inductive Dependent : (ι → ℙ K V) → Prop
| mk (f : ι → V) (hf : ∀ i : ι, f i ≠ 0) (h : ¬LinearIndependent K f) :
Dependent fun i => mk K (f i) (hf i)
#align projectivization.dependent Projectivization.Dependent
/-- A family of points in a projective space is dependent if and only if their
representatives are linearly dependent. -/
theorem dependent_iff : Dependent f ↔ ¬LinearIndependent K (Projectivization.rep ∘ f) := by
refine' ⟨_, fun h => _⟩
· rintro ⟨ff, hff, hh1⟩
contrapose! hh1
choose a ha using fun i : ι => exists_smul_eq_mk_rep K (ff i) (hff i)
convert hh1.units_smul a⁻¹
ext i
simp only [← ha, inv_smul_smul, Pi.smul_apply', Pi.inv_apply, Function.comp_apply]
· convert Dependent.mk _ _ h
· simp only [mk_rep, Function.comp_apply]
· exact fun i => rep_nonzero (f i)
#align projectivization.dependent_iff Projectivization.dependent_iff
/-- Dependence is the negation of independence. -/
theorem dependent_iff_not_independent : Dependent f ↔ ¬Independent f := by
rw [dependent_iff, independent_iff]
#align projectivization.dependent_iff_not_independent Projectivization.dependent_iff_not_independent
/-- Independence is the negation of dependence. -/
theorem independent_iff_not_dependent : Independent f ↔ ¬Dependent f := by
rw [dependent_iff_not_independent, Classical.not_not]
#align projectivization.independent_iff_not_dependent Projectivization.independent_iff_not_dependent
/-- Two points in a projective space are dependent if and only if they are equal. -/
@[simp]
theorem dependent_pair_iff_eq (u v : ℙ K V) : Dependent ![u, v] ↔ u = v := by
rw [dependent_iff_not_independent, independent_iff, linearIndependent_fin2,
Function.comp_apply, Matrix.cons_val_one, Matrix.head_cons, Ne.def]
simp only [Matrix.cons_val_zero, not_and, not_forall, Classical.not_not, Function.comp_apply,
← mk_eq_mk_iff' K _ _ (rep_nonzero u) (rep_nonzero v), mk_rep, imp_iff_right_iff]
exact Or.inl (rep_nonzero v)
#align projectivization.dependent_pair_iff_eq Projectivization.dependent_pair_iff_eq
/-- Two points in a projective space are independent if and only if the points are not equal. -/
@[simp]
theorem independent_pair_iff_neq (u v : ℙ K V) : Independent ![u, v] ↔ u ≠ v := by
| rw [independent_iff_not_dependent, dependent_pair_iff_eq u v] | /-- Two points in a projective space are independent if and only if the points are not equal. -/
@[simp]
theorem independent_pair_iff_neq (u v : ℙ K V) : Independent ![u, v] ↔ u ≠ v := by
| Mathlib.LinearAlgebra.Projectivization.Independence.117_0.owtLEGtk9UFDfW6 | /-- Two points in a projective space are independent if and only if the points are not equal. -/
@[simp]
theorem independent_pair_iff_neq (u v : ℙ K V) : Independent ![u, v] ↔ u ≠ v | Mathlib_LinearAlgebra_Projectivization_Independence |
α : Type u
β : Type v
γ : Type w
inst✝¹ : TopologicalSpace α
inst✝ : PartialOrder α
t : OrderClosedTopology α
⊢ IsClosed (diagonal α) | /-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro, Yury Kudryashov
-/
import Mathlib.Data.Set.Intervals.Pi
import Mathlib.Data.Set.Pointwise.Interval
import Mathlib.Order.Filter.Interval
import Mathlib.Tactic.TFAE
import Mathlib.Topology.Support
import Mathlib.Topology.Algebra.Order.LeftRight
#align_import topology.order.basic from "leanprover-community/mathlib"@"3efd324a3a31eaa40c9d5bfc669c4fafee5f9423"
/-!
# Theory of topology on ordered spaces
## Main definitions
The order topology on an ordered space is the topology generated by all open intervals (or
equivalently by those of the form `(-∞, a)` and `(b, +∞)`). We define it as `Preorder.topology α`.
However, we do *not* register it as an instance (as many existing ordered types already have
topologies, which would be equal but not definitionally equal to `Preorder.topology α`). Instead,
we introduce a class `OrderTopology α` (which is a `Prop`, also known as a mixin) saying that on
the type `α` having already a topological space structure and a preorder structure, the topological
structure is equal to the order topology.
We also introduce another (mixin) class `OrderClosedTopology α` saying that the set of points
`(x, y)` with `x ≤ y` is closed in the product space. This is automatically satisfied on a linear
order with the order topology.
We prove many basic properties of such topologies.
## Main statements
This file contains the proofs of the following facts. For exact requirements
(`OrderClosedTopology` vs `OrderTopology`, `Preorder` vs `PartialOrder` vs `LinearOrder` etc)
see their statements.
### Open / closed sets
* `isOpen_lt` : if `f` and `g` are continuous functions, then `{x | f x < g x}` is open;
* `isOpen_Iio`, `isOpen_Ioi`, `isOpen_Ioo` : open intervals are open;
* `isClosed_le` : if `f` and `g` are continuous functions, then `{x | f x ≤ g x}` is closed;
* `isClosed_Iic`, `isClosed_Ici`, `isClosed_Icc` : closed intervals are closed;
* `frontier_le_subset_eq`, `frontier_lt_subset_eq` : frontiers of both `{x | f x ≤ g x}`
and `{x | f x < g x}` are included by `{x | f x = g x}`;
* `exists_Ioc_subset_of_mem_nhds`, `exists_Ico_subset_of_mem_nhds` : if `x < y`, then any
neighborhood of `x` includes an interval `[x, z)` for some `z ∈ (x, y]`, and any neighborhood
of `y` includes an interval `(z, y]` for some `z ∈ [x, y)`.
### Convergence and inequalities
* `le_of_tendsto_of_tendsto` : if `f` converges to `a`, `g` converges to `b`, and eventually
`f x ≤ g x`, then `a ≤ b`
* `le_of_tendsto`, `ge_of_tendsto` : if `f` converges to `a` and eventually `f x ≤ b`
(resp., `b ≤ f x`), then `a ≤ b` (resp., `b ≤ a`); we also provide primed versions
that assume the inequalities to hold for all `x`.
### Min, max, `sSup` and `sInf`
* `Continuous.min`, `Continuous.max`: pointwise `min`/`max` of two continuous functions is
continuous.
* `Tendsto.min`, `Tendsto.max` : if `f` tends to `a` and `g` tends to `b`, then their pointwise
`min`/`max` tend to `min a b` and `max a b`, respectively.
* `tendsto_of_tendsto_of_tendsto_of_le_of_le` : theorem known as squeeze theorem,
sandwich theorem, theorem of Carabinieri, and two policemen (and a drunk) theorem; if `g` and `h`
both converge to `a`, and eventually `g x ≤ f x ≤ h x`, then `f` converges to `a`.
## Implementation notes
We do _not_ register the order topology as an instance on a preorder (or even on a linear order).
Indeed, on many such spaces, a topology has already been constructed in a different way (think
of the discrete spaces `ℕ` or `ℤ`, or `ℝ` that could inherit a topology as the completion of `ℚ`),
and is in general not defeq to the one generated by the intervals. We make it available as a
definition `Preorder.topology α` though, that can be registered as an instance when necessary, or
for specific types.
-/
open Set Filter TopologicalSpace Topology Function
open OrderDual (toDual ofDual)
universe u v w
variable {α : Type u} {β : Type v} {γ : Type w}
/-- If `α` is a topological space and a preorder, `ClosedIicTopology α` means that `Iic a` is
closed for all `a : α`. -/
class ClosedIicTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- For any `a`, the set `{b | b ≤ a}` is closed. -/
isClosed_le' (a : α) : IsClosed { b : α | b ≤ a }
export ClosedIicTopology (isClosed_le')
#align is_closed_le' ClosedIicTopology.isClosed_le'
/-- If `α` is a topological space and a preorder, `ClosedIciTopology α` means that `Ici a` is
closed for all `a : α`. -/
class ClosedIciTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- For any `a`, the set `{b | a ≤ b}` is closed. -/
isClosed_ge' (a : α) : IsClosed { b : α | a ≤ b }
export ClosedIciTopology (isClosed_ge')
#align is_closed_ge' ClosedIciTopology.isClosed_ge'
/-- A topology on a set which is both a topological space and a preorder is _order-closed_ if the
set of points `(x, y)` with `x ≤ y` is closed in the product space. We introduce this as a mixin.
This property is satisfied for the order topology on a linear order, but it can be satisfied more
generally, and suffices to derive many interesting properties relating order and topology. -/
class OrderClosedTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- The set `{ (x, y) | x ≤ y }` is a closed set. -/
isClosed_le' : IsClosed { p : α × α | p.1 ≤ p.2 }
#align order_closed_topology OrderClosedTopology
instance [TopologicalSpace α] [h : FirstCountableTopology α] : FirstCountableTopology αᵒᵈ := h
instance [TopologicalSpace α] [h : SecondCountableTopology α] : SecondCountableTopology αᵒᵈ := h
theorem Dense.orderDual [TopologicalSpace α] {s : Set α} (hs : Dense s) :
Dense (OrderDual.ofDual ⁻¹' s) :=
hs
#align dense.order_dual Dense.orderDual
section ClosedIicTopology
variable [TopologicalSpace α] [Preorder α] [t : ClosedIicTopology α]
instance : ClosedIciTopology αᵒᵈ where
isClosed_ge' a := isClosed_le' (α := α) a
theorem isClosed_Iic {a : α} : IsClosed (Iic a) :=
isClosed_le' a
#align is_closed_Iic isClosed_Iic
@[simp]
theorem closure_Iic (a : α) : closure (Iic a) = Iic a :=
isClosed_Iic.closure_eq
#align closure_Iic closure_Iic
theorem le_of_tendsto {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ᶠ c in x, f c ≤ b) : a ≤ b :=
(isClosed_le' b).mem_of_tendsto lim h
#align le_of_tendsto le_of_tendsto
theorem le_of_tendsto' {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ c, f c ≤ b) : a ≤ b :=
le_of_tendsto lim (eventually_of_forall h)
#align le_of_tendsto' le_of_tendsto'
end ClosedIicTopology
section ClosedIciTopology
variable [TopologicalSpace α] [Preorder α] [t : ClosedIciTopology α]
instance : ClosedIicTopology αᵒᵈ where
isClosed_le' a := isClosed_ge' (α := α) a
theorem isClosed_Ici {a : α} : IsClosed (Ici a) :=
isClosed_ge' a
#align is_closed_Ici isClosed_Ici
@[simp]
theorem closure_Ici (a : α) : closure (Ici a) = Ici a :=
isClosed_Ici.closure_eq
#align closure_Ici closure_Ici
theorem ge_of_tendsto {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ᶠ c in x, b ≤ f c) : b ≤ a :=
(isClosed_ge' b).mem_of_tendsto lim h
#align ge_of_tendsto ge_of_tendsto
theorem ge_of_tendsto' {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ c, b ≤ f c) : b ≤ a :=
ge_of_tendsto lim (eventually_of_forall h)
#align ge_of_tendsto' ge_of_tendsto'
end ClosedIciTopology
section OrderClosedTopology
section Preorder
variable [TopologicalSpace α] [Preorder α] [t : OrderClosedTopology α]
namespace Subtype
-- todo: add `OrderEmbedding.orderClosedTopology`
instance {p : α → Prop} : OrderClosedTopology (Subtype p) :=
have this : Continuous fun p : Subtype p × Subtype p => ((p.fst : α), (p.snd : α)) :=
continuous_subtype_val.prod_map continuous_subtype_val
OrderClosedTopology.mk (t.isClosed_le'.preimage this)
end Subtype
theorem isClosed_le_prod : IsClosed { p : α × α | p.1 ≤ p.2 } :=
t.isClosed_le'
#align is_closed_le_prod isClosed_le_prod
theorem isClosed_le [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
IsClosed { b | f b ≤ g b } :=
continuous_iff_isClosed.mp (hf.prod_mk hg) _ isClosed_le_prod
#align is_closed_le isClosed_le
instance : ClosedIicTopology α where
isClosed_le' _ := isClosed_le continuous_id continuous_const
instance : ClosedIciTopology α where
isClosed_ge' _ := isClosed_le continuous_const continuous_id
instance : OrderClosedTopology αᵒᵈ :=
⟨(OrderClosedTopology.isClosed_le' (α := α)).preimage continuous_swap⟩
theorem isClosed_Icc {a b : α} : IsClosed (Icc a b) :=
IsClosed.inter isClosed_Ici isClosed_Iic
#align is_closed_Icc isClosed_Icc
@[simp]
theorem closure_Icc (a b : α) : closure (Icc a b) = Icc a b :=
isClosed_Icc.closure_eq
#align closure_Icc closure_Icc
theorem le_of_tendsto_of_tendsto {f g : β → α} {b : Filter β} {a₁ a₂ : α} [NeBot b]
(hf : Tendsto f b (𝓝 a₁)) (hg : Tendsto g b (𝓝 a₂)) (h : f ≤ᶠ[b] g) : a₁ ≤ a₂ :=
have : Tendsto (fun b => (f b, g b)) b (𝓝 (a₁, a₂)) := hf.prod_mk_nhds hg
show (a₁, a₂) ∈ { p : α × α | p.1 ≤ p.2 } from t.isClosed_le'.mem_of_tendsto this h
#align le_of_tendsto_of_tendsto le_of_tendsto_of_tendsto
alias tendsto_le_of_eventuallyLE := le_of_tendsto_of_tendsto
#align tendsto_le_of_eventually_le tendsto_le_of_eventuallyLE
theorem le_of_tendsto_of_tendsto' {f g : β → α} {b : Filter β} {a₁ a₂ : α} [NeBot b]
(hf : Tendsto f b (𝓝 a₁)) (hg : Tendsto g b (𝓝 a₂)) (h : ∀ x, f x ≤ g x) : a₁ ≤ a₂ :=
le_of_tendsto_of_tendsto hf hg (eventually_of_forall h)
#align le_of_tendsto_of_tendsto' le_of_tendsto_of_tendsto'
@[simp]
theorem closure_le_eq [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
closure { b | f b ≤ g b } = { b | f b ≤ g b } :=
(isClosed_le hf hg).closure_eq
#align closure_le_eq closure_le_eq
theorem closure_lt_subset_le [TopologicalSpace β] {f g : β → α} (hf : Continuous f)
(hg : Continuous g) : closure { b | f b < g b } ⊆ { b | f b ≤ g b } :=
(closure_minimal fun _ => le_of_lt) <| isClosed_le hf hg
#align closure_lt_subset_le closure_lt_subset_le
theorem ContinuousWithinAt.closure_le [TopologicalSpace β] {f g : β → α} {s : Set β} {x : β}
(hx : x ∈ closure s) (hf : ContinuousWithinAt f s x) (hg : ContinuousWithinAt g s x)
(h : ∀ y ∈ s, f y ≤ g y) : f x ≤ g x :=
show (f x, g x) ∈ { p : α × α | p.1 ≤ p.2 } from
OrderClosedTopology.isClosed_le'.closure_subset ((hf.prod hg).mem_closure hx h)
#align continuous_within_at.closure_le ContinuousWithinAt.closure_le
/-- If `s` is a closed set and two functions `f` and `g` are continuous on `s`,
then the set `{x ∈ s | f x ≤ g x}` is a closed set. -/
theorem IsClosed.isClosed_le [TopologicalSpace β] {f g : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) (hg : ContinuousOn g s) : IsClosed ({ x ∈ s | f x ≤ g x }) :=
(hf.prod hg).preimage_isClosed_of_isClosed hs OrderClosedTopology.isClosed_le'
#align is_closed.is_closed_le IsClosed.isClosed_le
theorem le_on_closure [TopologicalSpace β] {f g : β → α} {s : Set β} (h : ∀ x ∈ s, f x ≤ g x)
(hf : ContinuousOn f (closure s)) (hg : ContinuousOn g (closure s)) ⦃x⦄ (hx : x ∈ closure s) :
f x ≤ g x :=
have : s ⊆ { y ∈ closure s | f y ≤ g y } := fun y hy => ⟨subset_closure hy, h y hy⟩
(closure_minimal this (isClosed_closure.isClosed_le hf hg) hx).2
#align le_on_closure le_on_closure
theorem IsClosed.epigraph [TopologicalSpace β] {f : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) : IsClosed { p : β × α | p.1 ∈ s ∧ f p.1 ≤ p.2 } :=
(hs.preimage continuous_fst).isClosed_le (hf.comp continuousOn_fst Subset.rfl) continuousOn_snd
#align is_closed.epigraph IsClosed.epigraph
theorem IsClosed.hypograph [TopologicalSpace β] {f : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) : IsClosed { p : β × α | p.1 ∈ s ∧ p.2 ≤ f p.1 } :=
(hs.preimage continuous_fst).isClosed_le continuousOn_snd (hf.comp continuousOn_fst Subset.rfl)
#align is_closed.hypograph IsClosed.hypograph
end Preorder
section PartialOrder
variable [TopologicalSpace α] [PartialOrder α] [t : OrderClosedTopology α]
-- see Note [lower instance priority]
instance (priority := 90) OrderClosedTopology.to_t2Space : T2Space α :=
t2_iff_isClosed_diagonal.2 <| by
| simpa only [diagonal, le_antisymm_iff] using
t.isClosed_le'.inter (isClosed_le continuous_snd continuous_fst) | instance (priority := 90) OrderClosedTopology.to_t2Space : T2Space α :=
t2_iff_isClosed_diagonal.2 <| by
| Mathlib.Topology.Order.Basic.286_0.Npdof1X5b8sCkZ2 | instance (priority | Mathlib_Topology_Order_Basic |
α : Type u
β : Type v
γ : Type w
inst✝³ : TopologicalSpace α
inst✝² : LinearOrder α
inst✝¹ : OrderClosedTopology α
inst✝ : TopologicalSpace β
f g : β → α
hf : Continuous f
hg : Continuous g
⊢ IsOpen {b | f b < g b} | /-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro, Yury Kudryashov
-/
import Mathlib.Data.Set.Intervals.Pi
import Mathlib.Data.Set.Pointwise.Interval
import Mathlib.Order.Filter.Interval
import Mathlib.Tactic.TFAE
import Mathlib.Topology.Support
import Mathlib.Topology.Algebra.Order.LeftRight
#align_import topology.order.basic from "leanprover-community/mathlib"@"3efd324a3a31eaa40c9d5bfc669c4fafee5f9423"
/-!
# Theory of topology on ordered spaces
## Main definitions
The order topology on an ordered space is the topology generated by all open intervals (or
equivalently by those of the form `(-∞, a)` and `(b, +∞)`). We define it as `Preorder.topology α`.
However, we do *not* register it as an instance (as many existing ordered types already have
topologies, which would be equal but not definitionally equal to `Preorder.topology α`). Instead,
we introduce a class `OrderTopology α` (which is a `Prop`, also known as a mixin) saying that on
the type `α` having already a topological space structure and a preorder structure, the topological
structure is equal to the order topology.
We also introduce another (mixin) class `OrderClosedTopology α` saying that the set of points
`(x, y)` with `x ≤ y` is closed in the product space. This is automatically satisfied on a linear
order with the order topology.
We prove many basic properties of such topologies.
## Main statements
This file contains the proofs of the following facts. For exact requirements
(`OrderClosedTopology` vs `OrderTopology`, `Preorder` vs `PartialOrder` vs `LinearOrder` etc)
see their statements.
### Open / closed sets
* `isOpen_lt` : if `f` and `g` are continuous functions, then `{x | f x < g x}` is open;
* `isOpen_Iio`, `isOpen_Ioi`, `isOpen_Ioo` : open intervals are open;
* `isClosed_le` : if `f` and `g` are continuous functions, then `{x | f x ≤ g x}` is closed;
* `isClosed_Iic`, `isClosed_Ici`, `isClosed_Icc` : closed intervals are closed;
* `frontier_le_subset_eq`, `frontier_lt_subset_eq` : frontiers of both `{x | f x ≤ g x}`
and `{x | f x < g x}` are included by `{x | f x = g x}`;
* `exists_Ioc_subset_of_mem_nhds`, `exists_Ico_subset_of_mem_nhds` : if `x < y`, then any
neighborhood of `x` includes an interval `[x, z)` for some `z ∈ (x, y]`, and any neighborhood
of `y` includes an interval `(z, y]` for some `z ∈ [x, y)`.
### Convergence and inequalities
* `le_of_tendsto_of_tendsto` : if `f` converges to `a`, `g` converges to `b`, and eventually
`f x ≤ g x`, then `a ≤ b`
* `le_of_tendsto`, `ge_of_tendsto` : if `f` converges to `a` and eventually `f x ≤ b`
(resp., `b ≤ f x`), then `a ≤ b` (resp., `b ≤ a`); we also provide primed versions
that assume the inequalities to hold for all `x`.
### Min, max, `sSup` and `sInf`
* `Continuous.min`, `Continuous.max`: pointwise `min`/`max` of two continuous functions is
continuous.
* `Tendsto.min`, `Tendsto.max` : if `f` tends to `a` and `g` tends to `b`, then their pointwise
`min`/`max` tend to `min a b` and `max a b`, respectively.
* `tendsto_of_tendsto_of_tendsto_of_le_of_le` : theorem known as squeeze theorem,
sandwich theorem, theorem of Carabinieri, and two policemen (and a drunk) theorem; if `g` and `h`
both converge to `a`, and eventually `g x ≤ f x ≤ h x`, then `f` converges to `a`.
## Implementation notes
We do _not_ register the order topology as an instance on a preorder (or even on a linear order).
Indeed, on many such spaces, a topology has already been constructed in a different way (think
of the discrete spaces `ℕ` or `ℤ`, or `ℝ` that could inherit a topology as the completion of `ℚ`),
and is in general not defeq to the one generated by the intervals. We make it available as a
definition `Preorder.topology α` though, that can be registered as an instance when necessary, or
for specific types.
-/
open Set Filter TopologicalSpace Topology Function
open OrderDual (toDual ofDual)
universe u v w
variable {α : Type u} {β : Type v} {γ : Type w}
/-- If `α` is a topological space and a preorder, `ClosedIicTopology α` means that `Iic a` is
closed for all `a : α`. -/
class ClosedIicTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- For any `a`, the set `{b | b ≤ a}` is closed. -/
isClosed_le' (a : α) : IsClosed { b : α | b ≤ a }
export ClosedIicTopology (isClosed_le')
#align is_closed_le' ClosedIicTopology.isClosed_le'
/-- If `α` is a topological space and a preorder, `ClosedIciTopology α` means that `Ici a` is
closed for all `a : α`. -/
class ClosedIciTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- For any `a`, the set `{b | a ≤ b}` is closed. -/
isClosed_ge' (a : α) : IsClosed { b : α | a ≤ b }
export ClosedIciTopology (isClosed_ge')
#align is_closed_ge' ClosedIciTopology.isClosed_ge'
/-- A topology on a set which is both a topological space and a preorder is _order-closed_ if the
set of points `(x, y)` with `x ≤ y` is closed in the product space. We introduce this as a mixin.
This property is satisfied for the order topology on a linear order, but it can be satisfied more
generally, and suffices to derive many interesting properties relating order and topology. -/
class OrderClosedTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- The set `{ (x, y) | x ≤ y }` is a closed set. -/
isClosed_le' : IsClosed { p : α × α | p.1 ≤ p.2 }
#align order_closed_topology OrderClosedTopology
instance [TopologicalSpace α] [h : FirstCountableTopology α] : FirstCountableTopology αᵒᵈ := h
instance [TopologicalSpace α] [h : SecondCountableTopology α] : SecondCountableTopology αᵒᵈ := h
theorem Dense.orderDual [TopologicalSpace α] {s : Set α} (hs : Dense s) :
Dense (OrderDual.ofDual ⁻¹' s) :=
hs
#align dense.order_dual Dense.orderDual
section ClosedIicTopology
variable [TopologicalSpace α] [Preorder α] [t : ClosedIicTopology α]
instance : ClosedIciTopology αᵒᵈ where
isClosed_ge' a := isClosed_le' (α := α) a
theorem isClosed_Iic {a : α} : IsClosed (Iic a) :=
isClosed_le' a
#align is_closed_Iic isClosed_Iic
@[simp]
theorem closure_Iic (a : α) : closure (Iic a) = Iic a :=
isClosed_Iic.closure_eq
#align closure_Iic closure_Iic
theorem le_of_tendsto {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ᶠ c in x, f c ≤ b) : a ≤ b :=
(isClosed_le' b).mem_of_tendsto lim h
#align le_of_tendsto le_of_tendsto
theorem le_of_tendsto' {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ c, f c ≤ b) : a ≤ b :=
le_of_tendsto lim (eventually_of_forall h)
#align le_of_tendsto' le_of_tendsto'
end ClosedIicTopology
section ClosedIciTopology
variable [TopologicalSpace α] [Preorder α] [t : ClosedIciTopology α]
instance : ClosedIicTopology αᵒᵈ where
isClosed_le' a := isClosed_ge' (α := α) a
theorem isClosed_Ici {a : α} : IsClosed (Ici a) :=
isClosed_ge' a
#align is_closed_Ici isClosed_Ici
@[simp]
theorem closure_Ici (a : α) : closure (Ici a) = Ici a :=
isClosed_Ici.closure_eq
#align closure_Ici closure_Ici
theorem ge_of_tendsto {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ᶠ c in x, b ≤ f c) : b ≤ a :=
(isClosed_ge' b).mem_of_tendsto lim h
#align ge_of_tendsto ge_of_tendsto
theorem ge_of_tendsto' {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ c, b ≤ f c) : b ≤ a :=
ge_of_tendsto lim (eventually_of_forall h)
#align ge_of_tendsto' ge_of_tendsto'
end ClosedIciTopology
section OrderClosedTopology
section Preorder
variable [TopologicalSpace α] [Preorder α] [t : OrderClosedTopology α]
namespace Subtype
-- todo: add `OrderEmbedding.orderClosedTopology`
instance {p : α → Prop} : OrderClosedTopology (Subtype p) :=
have this : Continuous fun p : Subtype p × Subtype p => ((p.fst : α), (p.snd : α)) :=
continuous_subtype_val.prod_map continuous_subtype_val
OrderClosedTopology.mk (t.isClosed_le'.preimage this)
end Subtype
theorem isClosed_le_prod : IsClosed { p : α × α | p.1 ≤ p.2 } :=
t.isClosed_le'
#align is_closed_le_prod isClosed_le_prod
theorem isClosed_le [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
IsClosed { b | f b ≤ g b } :=
continuous_iff_isClosed.mp (hf.prod_mk hg) _ isClosed_le_prod
#align is_closed_le isClosed_le
instance : ClosedIicTopology α where
isClosed_le' _ := isClosed_le continuous_id continuous_const
instance : ClosedIciTopology α where
isClosed_ge' _ := isClosed_le continuous_const continuous_id
instance : OrderClosedTopology αᵒᵈ :=
⟨(OrderClosedTopology.isClosed_le' (α := α)).preimage continuous_swap⟩
theorem isClosed_Icc {a b : α} : IsClosed (Icc a b) :=
IsClosed.inter isClosed_Ici isClosed_Iic
#align is_closed_Icc isClosed_Icc
@[simp]
theorem closure_Icc (a b : α) : closure (Icc a b) = Icc a b :=
isClosed_Icc.closure_eq
#align closure_Icc closure_Icc
theorem le_of_tendsto_of_tendsto {f g : β → α} {b : Filter β} {a₁ a₂ : α} [NeBot b]
(hf : Tendsto f b (𝓝 a₁)) (hg : Tendsto g b (𝓝 a₂)) (h : f ≤ᶠ[b] g) : a₁ ≤ a₂ :=
have : Tendsto (fun b => (f b, g b)) b (𝓝 (a₁, a₂)) := hf.prod_mk_nhds hg
show (a₁, a₂) ∈ { p : α × α | p.1 ≤ p.2 } from t.isClosed_le'.mem_of_tendsto this h
#align le_of_tendsto_of_tendsto le_of_tendsto_of_tendsto
alias tendsto_le_of_eventuallyLE := le_of_tendsto_of_tendsto
#align tendsto_le_of_eventually_le tendsto_le_of_eventuallyLE
theorem le_of_tendsto_of_tendsto' {f g : β → α} {b : Filter β} {a₁ a₂ : α} [NeBot b]
(hf : Tendsto f b (𝓝 a₁)) (hg : Tendsto g b (𝓝 a₂)) (h : ∀ x, f x ≤ g x) : a₁ ≤ a₂ :=
le_of_tendsto_of_tendsto hf hg (eventually_of_forall h)
#align le_of_tendsto_of_tendsto' le_of_tendsto_of_tendsto'
@[simp]
theorem closure_le_eq [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
closure { b | f b ≤ g b } = { b | f b ≤ g b } :=
(isClosed_le hf hg).closure_eq
#align closure_le_eq closure_le_eq
theorem closure_lt_subset_le [TopologicalSpace β] {f g : β → α} (hf : Continuous f)
(hg : Continuous g) : closure { b | f b < g b } ⊆ { b | f b ≤ g b } :=
(closure_minimal fun _ => le_of_lt) <| isClosed_le hf hg
#align closure_lt_subset_le closure_lt_subset_le
theorem ContinuousWithinAt.closure_le [TopologicalSpace β] {f g : β → α} {s : Set β} {x : β}
(hx : x ∈ closure s) (hf : ContinuousWithinAt f s x) (hg : ContinuousWithinAt g s x)
(h : ∀ y ∈ s, f y ≤ g y) : f x ≤ g x :=
show (f x, g x) ∈ { p : α × α | p.1 ≤ p.2 } from
OrderClosedTopology.isClosed_le'.closure_subset ((hf.prod hg).mem_closure hx h)
#align continuous_within_at.closure_le ContinuousWithinAt.closure_le
/-- If `s` is a closed set and two functions `f` and `g` are continuous on `s`,
then the set `{x ∈ s | f x ≤ g x}` is a closed set. -/
theorem IsClosed.isClosed_le [TopologicalSpace β] {f g : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) (hg : ContinuousOn g s) : IsClosed ({ x ∈ s | f x ≤ g x }) :=
(hf.prod hg).preimage_isClosed_of_isClosed hs OrderClosedTopology.isClosed_le'
#align is_closed.is_closed_le IsClosed.isClosed_le
theorem le_on_closure [TopologicalSpace β] {f g : β → α} {s : Set β} (h : ∀ x ∈ s, f x ≤ g x)
(hf : ContinuousOn f (closure s)) (hg : ContinuousOn g (closure s)) ⦃x⦄ (hx : x ∈ closure s) :
f x ≤ g x :=
have : s ⊆ { y ∈ closure s | f y ≤ g y } := fun y hy => ⟨subset_closure hy, h y hy⟩
(closure_minimal this (isClosed_closure.isClosed_le hf hg) hx).2
#align le_on_closure le_on_closure
theorem IsClosed.epigraph [TopologicalSpace β] {f : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) : IsClosed { p : β × α | p.1 ∈ s ∧ f p.1 ≤ p.2 } :=
(hs.preimage continuous_fst).isClosed_le (hf.comp continuousOn_fst Subset.rfl) continuousOn_snd
#align is_closed.epigraph IsClosed.epigraph
theorem IsClosed.hypograph [TopologicalSpace β] {f : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) : IsClosed { p : β × α | p.1 ∈ s ∧ p.2 ≤ f p.1 } :=
(hs.preimage continuous_fst).isClosed_le continuousOn_snd (hf.comp continuousOn_fst Subset.rfl)
#align is_closed.hypograph IsClosed.hypograph
end Preorder
section PartialOrder
variable [TopologicalSpace α] [PartialOrder α] [t : OrderClosedTopology α]
-- see Note [lower instance priority]
instance (priority := 90) OrderClosedTopology.to_t2Space : T2Space α :=
t2_iff_isClosed_diagonal.2 <| by
simpa only [diagonal, le_antisymm_iff] using
t.isClosed_le'.inter (isClosed_le continuous_snd continuous_fst)
#align order_closed_topology.to_t2_space OrderClosedTopology.to_t2Space
end PartialOrder
section LinearOrder
variable [TopologicalSpace α] [LinearOrder α] [OrderClosedTopology α]
theorem isOpen_lt [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
IsOpen { b | f b < g b } := by
| simpa only [lt_iff_not_le] using (isClosed_le hg hf).isOpen_compl | theorem isOpen_lt [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
IsOpen { b | f b < g b } := by
| Mathlib.Topology.Order.Basic.298_0.Npdof1X5b8sCkZ2 | theorem isOpen_lt [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
IsOpen { b | f b < g b } | Mathlib_Topology_Order_Basic |
α : Type u
β : Type v
γ : Type w
inst✝² : TopologicalSpace α
inst✝¹ : LinearOrder α
inst✝ : OrderClosedTopology α
a b : α
⊢ Ioo a b ⊆ closure (interior (Ioo a b)) | /-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro, Yury Kudryashov
-/
import Mathlib.Data.Set.Intervals.Pi
import Mathlib.Data.Set.Pointwise.Interval
import Mathlib.Order.Filter.Interval
import Mathlib.Tactic.TFAE
import Mathlib.Topology.Support
import Mathlib.Topology.Algebra.Order.LeftRight
#align_import topology.order.basic from "leanprover-community/mathlib"@"3efd324a3a31eaa40c9d5bfc669c4fafee5f9423"
/-!
# Theory of topology on ordered spaces
## Main definitions
The order topology on an ordered space is the topology generated by all open intervals (or
equivalently by those of the form `(-∞, a)` and `(b, +∞)`). We define it as `Preorder.topology α`.
However, we do *not* register it as an instance (as many existing ordered types already have
topologies, which would be equal but not definitionally equal to `Preorder.topology α`). Instead,
we introduce a class `OrderTopology α` (which is a `Prop`, also known as a mixin) saying that on
the type `α` having already a topological space structure and a preorder structure, the topological
structure is equal to the order topology.
We also introduce another (mixin) class `OrderClosedTopology α` saying that the set of points
`(x, y)` with `x ≤ y` is closed in the product space. This is automatically satisfied on a linear
order with the order topology.
We prove many basic properties of such topologies.
## Main statements
This file contains the proofs of the following facts. For exact requirements
(`OrderClosedTopology` vs `OrderTopology`, `Preorder` vs `PartialOrder` vs `LinearOrder` etc)
see their statements.
### Open / closed sets
* `isOpen_lt` : if `f` and `g` are continuous functions, then `{x | f x < g x}` is open;
* `isOpen_Iio`, `isOpen_Ioi`, `isOpen_Ioo` : open intervals are open;
* `isClosed_le` : if `f` and `g` are continuous functions, then `{x | f x ≤ g x}` is closed;
* `isClosed_Iic`, `isClosed_Ici`, `isClosed_Icc` : closed intervals are closed;
* `frontier_le_subset_eq`, `frontier_lt_subset_eq` : frontiers of both `{x | f x ≤ g x}`
and `{x | f x < g x}` are included by `{x | f x = g x}`;
* `exists_Ioc_subset_of_mem_nhds`, `exists_Ico_subset_of_mem_nhds` : if `x < y`, then any
neighborhood of `x` includes an interval `[x, z)` for some `z ∈ (x, y]`, and any neighborhood
of `y` includes an interval `(z, y]` for some `z ∈ [x, y)`.
### Convergence and inequalities
* `le_of_tendsto_of_tendsto` : if `f` converges to `a`, `g` converges to `b`, and eventually
`f x ≤ g x`, then `a ≤ b`
* `le_of_tendsto`, `ge_of_tendsto` : if `f` converges to `a` and eventually `f x ≤ b`
(resp., `b ≤ f x`), then `a ≤ b` (resp., `b ≤ a`); we also provide primed versions
that assume the inequalities to hold for all `x`.
### Min, max, `sSup` and `sInf`
* `Continuous.min`, `Continuous.max`: pointwise `min`/`max` of two continuous functions is
continuous.
* `Tendsto.min`, `Tendsto.max` : if `f` tends to `a` and `g` tends to `b`, then their pointwise
`min`/`max` tend to `min a b` and `max a b`, respectively.
* `tendsto_of_tendsto_of_tendsto_of_le_of_le` : theorem known as squeeze theorem,
sandwich theorem, theorem of Carabinieri, and two policemen (and a drunk) theorem; if `g` and `h`
both converge to `a`, and eventually `g x ≤ f x ≤ h x`, then `f` converges to `a`.
## Implementation notes
We do _not_ register the order topology as an instance on a preorder (or even on a linear order).
Indeed, on many such spaces, a topology has already been constructed in a different way (think
of the discrete spaces `ℕ` or `ℤ`, or `ℝ` that could inherit a topology as the completion of `ℚ`),
and is in general not defeq to the one generated by the intervals. We make it available as a
definition `Preorder.topology α` though, that can be registered as an instance when necessary, or
for specific types.
-/
open Set Filter TopologicalSpace Topology Function
open OrderDual (toDual ofDual)
universe u v w
variable {α : Type u} {β : Type v} {γ : Type w}
/-- If `α` is a topological space and a preorder, `ClosedIicTopology α` means that `Iic a` is
closed for all `a : α`. -/
class ClosedIicTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- For any `a`, the set `{b | b ≤ a}` is closed. -/
isClosed_le' (a : α) : IsClosed { b : α | b ≤ a }
export ClosedIicTopology (isClosed_le')
#align is_closed_le' ClosedIicTopology.isClosed_le'
/-- If `α` is a topological space and a preorder, `ClosedIciTopology α` means that `Ici a` is
closed for all `a : α`. -/
class ClosedIciTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- For any `a`, the set `{b | a ≤ b}` is closed. -/
isClosed_ge' (a : α) : IsClosed { b : α | a ≤ b }
export ClosedIciTopology (isClosed_ge')
#align is_closed_ge' ClosedIciTopology.isClosed_ge'
/-- A topology on a set which is both a topological space and a preorder is _order-closed_ if the
set of points `(x, y)` with `x ≤ y` is closed in the product space. We introduce this as a mixin.
This property is satisfied for the order topology on a linear order, but it can be satisfied more
generally, and suffices to derive many interesting properties relating order and topology. -/
class OrderClosedTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- The set `{ (x, y) | x ≤ y }` is a closed set. -/
isClosed_le' : IsClosed { p : α × α | p.1 ≤ p.2 }
#align order_closed_topology OrderClosedTopology
instance [TopologicalSpace α] [h : FirstCountableTopology α] : FirstCountableTopology αᵒᵈ := h
instance [TopologicalSpace α] [h : SecondCountableTopology α] : SecondCountableTopology αᵒᵈ := h
theorem Dense.orderDual [TopologicalSpace α] {s : Set α} (hs : Dense s) :
Dense (OrderDual.ofDual ⁻¹' s) :=
hs
#align dense.order_dual Dense.orderDual
section ClosedIicTopology
variable [TopologicalSpace α] [Preorder α] [t : ClosedIicTopology α]
instance : ClosedIciTopology αᵒᵈ where
isClosed_ge' a := isClosed_le' (α := α) a
theorem isClosed_Iic {a : α} : IsClosed (Iic a) :=
isClosed_le' a
#align is_closed_Iic isClosed_Iic
@[simp]
theorem closure_Iic (a : α) : closure (Iic a) = Iic a :=
isClosed_Iic.closure_eq
#align closure_Iic closure_Iic
theorem le_of_tendsto {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ᶠ c in x, f c ≤ b) : a ≤ b :=
(isClosed_le' b).mem_of_tendsto lim h
#align le_of_tendsto le_of_tendsto
theorem le_of_tendsto' {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ c, f c ≤ b) : a ≤ b :=
le_of_tendsto lim (eventually_of_forall h)
#align le_of_tendsto' le_of_tendsto'
end ClosedIicTopology
section ClosedIciTopology
variable [TopologicalSpace α] [Preorder α] [t : ClosedIciTopology α]
instance : ClosedIicTopology αᵒᵈ where
isClosed_le' a := isClosed_ge' (α := α) a
theorem isClosed_Ici {a : α} : IsClosed (Ici a) :=
isClosed_ge' a
#align is_closed_Ici isClosed_Ici
@[simp]
theorem closure_Ici (a : α) : closure (Ici a) = Ici a :=
isClosed_Ici.closure_eq
#align closure_Ici closure_Ici
theorem ge_of_tendsto {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ᶠ c in x, b ≤ f c) : b ≤ a :=
(isClosed_ge' b).mem_of_tendsto lim h
#align ge_of_tendsto ge_of_tendsto
theorem ge_of_tendsto' {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ c, b ≤ f c) : b ≤ a :=
ge_of_tendsto lim (eventually_of_forall h)
#align ge_of_tendsto' ge_of_tendsto'
end ClosedIciTopology
section OrderClosedTopology
section Preorder
variable [TopologicalSpace α] [Preorder α] [t : OrderClosedTopology α]
namespace Subtype
-- todo: add `OrderEmbedding.orderClosedTopology`
instance {p : α → Prop} : OrderClosedTopology (Subtype p) :=
have this : Continuous fun p : Subtype p × Subtype p => ((p.fst : α), (p.snd : α)) :=
continuous_subtype_val.prod_map continuous_subtype_val
OrderClosedTopology.mk (t.isClosed_le'.preimage this)
end Subtype
theorem isClosed_le_prod : IsClosed { p : α × α | p.1 ≤ p.2 } :=
t.isClosed_le'
#align is_closed_le_prod isClosed_le_prod
theorem isClosed_le [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
IsClosed { b | f b ≤ g b } :=
continuous_iff_isClosed.mp (hf.prod_mk hg) _ isClosed_le_prod
#align is_closed_le isClosed_le
instance : ClosedIicTopology α where
isClosed_le' _ := isClosed_le continuous_id continuous_const
instance : ClosedIciTopology α where
isClosed_ge' _ := isClosed_le continuous_const continuous_id
instance : OrderClosedTopology αᵒᵈ :=
⟨(OrderClosedTopology.isClosed_le' (α := α)).preimage continuous_swap⟩
theorem isClosed_Icc {a b : α} : IsClosed (Icc a b) :=
IsClosed.inter isClosed_Ici isClosed_Iic
#align is_closed_Icc isClosed_Icc
@[simp]
theorem closure_Icc (a b : α) : closure (Icc a b) = Icc a b :=
isClosed_Icc.closure_eq
#align closure_Icc closure_Icc
theorem le_of_tendsto_of_tendsto {f g : β → α} {b : Filter β} {a₁ a₂ : α} [NeBot b]
(hf : Tendsto f b (𝓝 a₁)) (hg : Tendsto g b (𝓝 a₂)) (h : f ≤ᶠ[b] g) : a₁ ≤ a₂ :=
have : Tendsto (fun b => (f b, g b)) b (𝓝 (a₁, a₂)) := hf.prod_mk_nhds hg
show (a₁, a₂) ∈ { p : α × α | p.1 ≤ p.2 } from t.isClosed_le'.mem_of_tendsto this h
#align le_of_tendsto_of_tendsto le_of_tendsto_of_tendsto
alias tendsto_le_of_eventuallyLE := le_of_tendsto_of_tendsto
#align tendsto_le_of_eventually_le tendsto_le_of_eventuallyLE
theorem le_of_tendsto_of_tendsto' {f g : β → α} {b : Filter β} {a₁ a₂ : α} [NeBot b]
(hf : Tendsto f b (𝓝 a₁)) (hg : Tendsto g b (𝓝 a₂)) (h : ∀ x, f x ≤ g x) : a₁ ≤ a₂ :=
le_of_tendsto_of_tendsto hf hg (eventually_of_forall h)
#align le_of_tendsto_of_tendsto' le_of_tendsto_of_tendsto'
@[simp]
theorem closure_le_eq [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
closure { b | f b ≤ g b } = { b | f b ≤ g b } :=
(isClosed_le hf hg).closure_eq
#align closure_le_eq closure_le_eq
theorem closure_lt_subset_le [TopologicalSpace β] {f g : β → α} (hf : Continuous f)
(hg : Continuous g) : closure { b | f b < g b } ⊆ { b | f b ≤ g b } :=
(closure_minimal fun _ => le_of_lt) <| isClosed_le hf hg
#align closure_lt_subset_le closure_lt_subset_le
theorem ContinuousWithinAt.closure_le [TopologicalSpace β] {f g : β → α} {s : Set β} {x : β}
(hx : x ∈ closure s) (hf : ContinuousWithinAt f s x) (hg : ContinuousWithinAt g s x)
(h : ∀ y ∈ s, f y ≤ g y) : f x ≤ g x :=
show (f x, g x) ∈ { p : α × α | p.1 ≤ p.2 } from
OrderClosedTopology.isClosed_le'.closure_subset ((hf.prod hg).mem_closure hx h)
#align continuous_within_at.closure_le ContinuousWithinAt.closure_le
/-- If `s` is a closed set and two functions `f` and `g` are continuous on `s`,
then the set `{x ∈ s | f x ≤ g x}` is a closed set. -/
theorem IsClosed.isClosed_le [TopologicalSpace β] {f g : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) (hg : ContinuousOn g s) : IsClosed ({ x ∈ s | f x ≤ g x }) :=
(hf.prod hg).preimage_isClosed_of_isClosed hs OrderClosedTopology.isClosed_le'
#align is_closed.is_closed_le IsClosed.isClosed_le
theorem le_on_closure [TopologicalSpace β] {f g : β → α} {s : Set β} (h : ∀ x ∈ s, f x ≤ g x)
(hf : ContinuousOn f (closure s)) (hg : ContinuousOn g (closure s)) ⦃x⦄ (hx : x ∈ closure s) :
f x ≤ g x :=
have : s ⊆ { y ∈ closure s | f y ≤ g y } := fun y hy => ⟨subset_closure hy, h y hy⟩
(closure_minimal this (isClosed_closure.isClosed_le hf hg) hx).2
#align le_on_closure le_on_closure
theorem IsClosed.epigraph [TopologicalSpace β] {f : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) : IsClosed { p : β × α | p.1 ∈ s ∧ f p.1 ≤ p.2 } :=
(hs.preimage continuous_fst).isClosed_le (hf.comp continuousOn_fst Subset.rfl) continuousOn_snd
#align is_closed.epigraph IsClosed.epigraph
theorem IsClosed.hypograph [TopologicalSpace β] {f : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) : IsClosed { p : β × α | p.1 ∈ s ∧ p.2 ≤ f p.1 } :=
(hs.preimage continuous_fst).isClosed_le continuousOn_snd (hf.comp continuousOn_fst Subset.rfl)
#align is_closed.hypograph IsClosed.hypograph
end Preorder
section PartialOrder
variable [TopologicalSpace α] [PartialOrder α] [t : OrderClosedTopology α]
-- see Note [lower instance priority]
instance (priority := 90) OrderClosedTopology.to_t2Space : T2Space α :=
t2_iff_isClosed_diagonal.2 <| by
simpa only [diagonal, le_antisymm_iff] using
t.isClosed_le'.inter (isClosed_le continuous_snd continuous_fst)
#align order_closed_topology.to_t2_space OrderClosedTopology.to_t2Space
end PartialOrder
section LinearOrder
variable [TopologicalSpace α] [LinearOrder α] [OrderClosedTopology α]
theorem isOpen_lt [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
IsOpen { b | f b < g b } := by
simpa only [lt_iff_not_le] using (isClosed_le hg hf).isOpen_compl
#align is_open_lt isOpen_lt
theorem isOpen_lt_prod : IsOpen { p : α × α | p.1 < p.2 } :=
isOpen_lt continuous_fst continuous_snd
#align is_open_lt_prod isOpen_lt_prod
variable {a b : α}
theorem isOpen_Iio : IsOpen (Iio a) :=
isOpen_lt continuous_id continuous_const
#align is_open_Iio isOpen_Iio
theorem isOpen_Ioi : IsOpen (Ioi a) :=
isOpen_lt continuous_const continuous_id
#align is_open_Ioi isOpen_Ioi
theorem isOpen_Ioo : IsOpen (Ioo a b) :=
IsOpen.inter isOpen_Ioi isOpen_Iio
#align is_open_Ioo isOpen_Ioo
@[simp]
theorem interior_Ioi : interior (Ioi a) = Ioi a :=
isOpen_Ioi.interior_eq
#align interior_Ioi interior_Ioi
@[simp]
theorem interior_Iio : interior (Iio a) = Iio a :=
isOpen_Iio.interior_eq
#align interior_Iio interior_Iio
@[simp]
theorem interior_Ioo : interior (Ioo a b) = Ioo a b :=
isOpen_Ioo.interior_eq
#align interior_Ioo interior_Ioo
theorem Ioo_subset_closure_interior : Ioo a b ⊆ closure (interior (Ioo a b)) := by
| simp only [interior_Ioo, subset_closure] | theorem Ioo_subset_closure_interior : Ioo a b ⊆ closure (interior (Ioo a b)) := by
| Mathlib.Topology.Order.Basic.336_0.Npdof1X5b8sCkZ2 | theorem Ioo_subset_closure_interior : Ioo a b ⊆ closure (interior (Ioo a b)) | Mathlib_Topology_Order_Basic |
α : Type u
β : Type v
γ : Type w
inst✝³ : TopologicalSpace α
inst✝² : LinearOrder α
inst✝¹ : OrderClosedTopology α
a✝ b✝ : α
inst✝ : TopologicalSpace γ
a b c : α
H : b ∈ Ico a c
⊢ Iio c ∩ Ioi b ⊆ Ioo a c | /-
Copyright (c) 2017 Johannes Hölzl. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Johannes Hölzl, Mario Carneiro, Yury Kudryashov
-/
import Mathlib.Data.Set.Intervals.Pi
import Mathlib.Data.Set.Pointwise.Interval
import Mathlib.Order.Filter.Interval
import Mathlib.Tactic.TFAE
import Mathlib.Topology.Support
import Mathlib.Topology.Algebra.Order.LeftRight
#align_import topology.order.basic from "leanprover-community/mathlib"@"3efd324a3a31eaa40c9d5bfc669c4fafee5f9423"
/-!
# Theory of topology on ordered spaces
## Main definitions
The order topology on an ordered space is the topology generated by all open intervals (or
equivalently by those of the form `(-∞, a)` and `(b, +∞)`). We define it as `Preorder.topology α`.
However, we do *not* register it as an instance (as many existing ordered types already have
topologies, which would be equal but not definitionally equal to `Preorder.topology α`). Instead,
we introduce a class `OrderTopology α` (which is a `Prop`, also known as a mixin) saying that on
the type `α` having already a topological space structure and a preorder structure, the topological
structure is equal to the order topology.
We also introduce another (mixin) class `OrderClosedTopology α` saying that the set of points
`(x, y)` with `x ≤ y` is closed in the product space. This is automatically satisfied on a linear
order with the order topology.
We prove many basic properties of such topologies.
## Main statements
This file contains the proofs of the following facts. For exact requirements
(`OrderClosedTopology` vs `OrderTopology`, `Preorder` vs `PartialOrder` vs `LinearOrder` etc)
see their statements.
### Open / closed sets
* `isOpen_lt` : if `f` and `g` are continuous functions, then `{x | f x < g x}` is open;
* `isOpen_Iio`, `isOpen_Ioi`, `isOpen_Ioo` : open intervals are open;
* `isClosed_le` : if `f` and `g` are continuous functions, then `{x | f x ≤ g x}` is closed;
* `isClosed_Iic`, `isClosed_Ici`, `isClosed_Icc` : closed intervals are closed;
* `frontier_le_subset_eq`, `frontier_lt_subset_eq` : frontiers of both `{x | f x ≤ g x}`
and `{x | f x < g x}` are included by `{x | f x = g x}`;
* `exists_Ioc_subset_of_mem_nhds`, `exists_Ico_subset_of_mem_nhds` : if `x < y`, then any
neighborhood of `x` includes an interval `[x, z)` for some `z ∈ (x, y]`, and any neighborhood
of `y` includes an interval `(z, y]` for some `z ∈ [x, y)`.
### Convergence and inequalities
* `le_of_tendsto_of_tendsto` : if `f` converges to `a`, `g` converges to `b`, and eventually
`f x ≤ g x`, then `a ≤ b`
* `le_of_tendsto`, `ge_of_tendsto` : if `f` converges to `a` and eventually `f x ≤ b`
(resp., `b ≤ f x`), then `a ≤ b` (resp., `b ≤ a`); we also provide primed versions
that assume the inequalities to hold for all `x`.
### Min, max, `sSup` and `sInf`
* `Continuous.min`, `Continuous.max`: pointwise `min`/`max` of two continuous functions is
continuous.
* `Tendsto.min`, `Tendsto.max` : if `f` tends to `a` and `g` tends to `b`, then their pointwise
`min`/`max` tend to `min a b` and `max a b`, respectively.
* `tendsto_of_tendsto_of_tendsto_of_le_of_le` : theorem known as squeeze theorem,
sandwich theorem, theorem of Carabinieri, and two policemen (and a drunk) theorem; if `g` and `h`
both converge to `a`, and eventually `g x ≤ f x ≤ h x`, then `f` converges to `a`.
## Implementation notes
We do _not_ register the order topology as an instance on a preorder (or even on a linear order).
Indeed, on many such spaces, a topology has already been constructed in a different way (think
of the discrete spaces `ℕ` or `ℤ`, or `ℝ` that could inherit a topology as the completion of `ℚ`),
and is in general not defeq to the one generated by the intervals. We make it available as a
definition `Preorder.topology α` though, that can be registered as an instance when necessary, or
for specific types.
-/
open Set Filter TopologicalSpace Topology Function
open OrderDual (toDual ofDual)
universe u v w
variable {α : Type u} {β : Type v} {γ : Type w}
/-- If `α` is a topological space and a preorder, `ClosedIicTopology α` means that `Iic a` is
closed for all `a : α`. -/
class ClosedIicTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- For any `a`, the set `{b | b ≤ a}` is closed. -/
isClosed_le' (a : α) : IsClosed { b : α | b ≤ a }
export ClosedIicTopology (isClosed_le')
#align is_closed_le' ClosedIicTopology.isClosed_le'
/-- If `α` is a topological space and a preorder, `ClosedIciTopology α` means that `Ici a` is
closed for all `a : α`. -/
class ClosedIciTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- For any `a`, the set `{b | a ≤ b}` is closed. -/
isClosed_ge' (a : α) : IsClosed { b : α | a ≤ b }
export ClosedIciTopology (isClosed_ge')
#align is_closed_ge' ClosedIciTopology.isClosed_ge'
/-- A topology on a set which is both a topological space and a preorder is _order-closed_ if the
set of points `(x, y)` with `x ≤ y` is closed in the product space. We introduce this as a mixin.
This property is satisfied for the order topology on a linear order, but it can be satisfied more
generally, and suffices to derive many interesting properties relating order and topology. -/
class OrderClosedTopology (α : Type*) [TopologicalSpace α] [Preorder α] : Prop where
/-- The set `{ (x, y) | x ≤ y }` is a closed set. -/
isClosed_le' : IsClosed { p : α × α | p.1 ≤ p.2 }
#align order_closed_topology OrderClosedTopology
instance [TopologicalSpace α] [h : FirstCountableTopology α] : FirstCountableTopology αᵒᵈ := h
instance [TopologicalSpace α] [h : SecondCountableTopology α] : SecondCountableTopology αᵒᵈ := h
theorem Dense.orderDual [TopologicalSpace α] {s : Set α} (hs : Dense s) :
Dense (OrderDual.ofDual ⁻¹' s) :=
hs
#align dense.order_dual Dense.orderDual
section ClosedIicTopology
variable [TopologicalSpace α] [Preorder α] [t : ClosedIicTopology α]
instance : ClosedIciTopology αᵒᵈ where
isClosed_ge' a := isClosed_le' (α := α) a
theorem isClosed_Iic {a : α} : IsClosed (Iic a) :=
isClosed_le' a
#align is_closed_Iic isClosed_Iic
@[simp]
theorem closure_Iic (a : α) : closure (Iic a) = Iic a :=
isClosed_Iic.closure_eq
#align closure_Iic closure_Iic
theorem le_of_tendsto {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ᶠ c in x, f c ≤ b) : a ≤ b :=
(isClosed_le' b).mem_of_tendsto lim h
#align le_of_tendsto le_of_tendsto
theorem le_of_tendsto' {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ c, f c ≤ b) : a ≤ b :=
le_of_tendsto lim (eventually_of_forall h)
#align le_of_tendsto' le_of_tendsto'
end ClosedIicTopology
section ClosedIciTopology
variable [TopologicalSpace α] [Preorder α] [t : ClosedIciTopology α]
instance : ClosedIicTopology αᵒᵈ where
isClosed_le' a := isClosed_ge' (α := α) a
theorem isClosed_Ici {a : α} : IsClosed (Ici a) :=
isClosed_ge' a
#align is_closed_Ici isClosed_Ici
@[simp]
theorem closure_Ici (a : α) : closure (Ici a) = Ici a :=
isClosed_Ici.closure_eq
#align closure_Ici closure_Ici
theorem ge_of_tendsto {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ᶠ c in x, b ≤ f c) : b ≤ a :=
(isClosed_ge' b).mem_of_tendsto lim h
#align ge_of_tendsto ge_of_tendsto
theorem ge_of_tendsto' {f : β → α} {a b : α} {x : Filter β} [NeBot x] (lim : Tendsto f x (𝓝 a))
(h : ∀ c, b ≤ f c) : b ≤ a :=
ge_of_tendsto lim (eventually_of_forall h)
#align ge_of_tendsto' ge_of_tendsto'
end ClosedIciTopology
section OrderClosedTopology
section Preorder
variable [TopologicalSpace α] [Preorder α] [t : OrderClosedTopology α]
namespace Subtype
-- todo: add `OrderEmbedding.orderClosedTopology`
instance {p : α → Prop} : OrderClosedTopology (Subtype p) :=
have this : Continuous fun p : Subtype p × Subtype p => ((p.fst : α), (p.snd : α)) :=
continuous_subtype_val.prod_map continuous_subtype_val
OrderClosedTopology.mk (t.isClosed_le'.preimage this)
end Subtype
theorem isClosed_le_prod : IsClosed { p : α × α | p.1 ≤ p.2 } :=
t.isClosed_le'
#align is_closed_le_prod isClosed_le_prod
theorem isClosed_le [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
IsClosed { b | f b ≤ g b } :=
continuous_iff_isClosed.mp (hf.prod_mk hg) _ isClosed_le_prod
#align is_closed_le isClosed_le
instance : ClosedIicTopology α where
isClosed_le' _ := isClosed_le continuous_id continuous_const
instance : ClosedIciTopology α where
isClosed_ge' _ := isClosed_le continuous_const continuous_id
instance : OrderClosedTopology αᵒᵈ :=
⟨(OrderClosedTopology.isClosed_le' (α := α)).preimage continuous_swap⟩
theorem isClosed_Icc {a b : α} : IsClosed (Icc a b) :=
IsClosed.inter isClosed_Ici isClosed_Iic
#align is_closed_Icc isClosed_Icc
@[simp]
theorem closure_Icc (a b : α) : closure (Icc a b) = Icc a b :=
isClosed_Icc.closure_eq
#align closure_Icc closure_Icc
theorem le_of_tendsto_of_tendsto {f g : β → α} {b : Filter β} {a₁ a₂ : α} [NeBot b]
(hf : Tendsto f b (𝓝 a₁)) (hg : Tendsto g b (𝓝 a₂)) (h : f ≤ᶠ[b] g) : a₁ ≤ a₂ :=
have : Tendsto (fun b => (f b, g b)) b (𝓝 (a₁, a₂)) := hf.prod_mk_nhds hg
show (a₁, a₂) ∈ { p : α × α | p.1 ≤ p.2 } from t.isClosed_le'.mem_of_tendsto this h
#align le_of_tendsto_of_tendsto le_of_tendsto_of_tendsto
alias tendsto_le_of_eventuallyLE := le_of_tendsto_of_tendsto
#align tendsto_le_of_eventually_le tendsto_le_of_eventuallyLE
theorem le_of_tendsto_of_tendsto' {f g : β → α} {b : Filter β} {a₁ a₂ : α} [NeBot b]
(hf : Tendsto f b (𝓝 a₁)) (hg : Tendsto g b (𝓝 a₂)) (h : ∀ x, f x ≤ g x) : a₁ ≤ a₂ :=
le_of_tendsto_of_tendsto hf hg (eventually_of_forall h)
#align le_of_tendsto_of_tendsto' le_of_tendsto_of_tendsto'
@[simp]
theorem closure_le_eq [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
closure { b | f b ≤ g b } = { b | f b ≤ g b } :=
(isClosed_le hf hg).closure_eq
#align closure_le_eq closure_le_eq
theorem closure_lt_subset_le [TopologicalSpace β] {f g : β → α} (hf : Continuous f)
(hg : Continuous g) : closure { b | f b < g b } ⊆ { b | f b ≤ g b } :=
(closure_minimal fun _ => le_of_lt) <| isClosed_le hf hg
#align closure_lt_subset_le closure_lt_subset_le
theorem ContinuousWithinAt.closure_le [TopologicalSpace β] {f g : β → α} {s : Set β} {x : β}
(hx : x ∈ closure s) (hf : ContinuousWithinAt f s x) (hg : ContinuousWithinAt g s x)
(h : ∀ y ∈ s, f y ≤ g y) : f x ≤ g x :=
show (f x, g x) ∈ { p : α × α | p.1 ≤ p.2 } from
OrderClosedTopology.isClosed_le'.closure_subset ((hf.prod hg).mem_closure hx h)
#align continuous_within_at.closure_le ContinuousWithinAt.closure_le
/-- If `s` is a closed set and two functions `f` and `g` are continuous on `s`,
then the set `{x ∈ s | f x ≤ g x}` is a closed set. -/
theorem IsClosed.isClosed_le [TopologicalSpace β] {f g : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) (hg : ContinuousOn g s) : IsClosed ({ x ∈ s | f x ≤ g x }) :=
(hf.prod hg).preimage_isClosed_of_isClosed hs OrderClosedTopology.isClosed_le'
#align is_closed.is_closed_le IsClosed.isClosed_le
theorem le_on_closure [TopologicalSpace β] {f g : β → α} {s : Set β} (h : ∀ x ∈ s, f x ≤ g x)
(hf : ContinuousOn f (closure s)) (hg : ContinuousOn g (closure s)) ⦃x⦄ (hx : x ∈ closure s) :
f x ≤ g x :=
have : s ⊆ { y ∈ closure s | f y ≤ g y } := fun y hy => ⟨subset_closure hy, h y hy⟩
(closure_minimal this (isClosed_closure.isClosed_le hf hg) hx).2
#align le_on_closure le_on_closure
theorem IsClosed.epigraph [TopologicalSpace β] {f : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) : IsClosed { p : β × α | p.1 ∈ s ∧ f p.1 ≤ p.2 } :=
(hs.preimage continuous_fst).isClosed_le (hf.comp continuousOn_fst Subset.rfl) continuousOn_snd
#align is_closed.epigraph IsClosed.epigraph
theorem IsClosed.hypograph [TopologicalSpace β] {f : β → α} {s : Set β} (hs : IsClosed s)
(hf : ContinuousOn f s) : IsClosed { p : β × α | p.1 ∈ s ∧ p.2 ≤ f p.1 } :=
(hs.preimage continuous_fst).isClosed_le continuousOn_snd (hf.comp continuousOn_fst Subset.rfl)
#align is_closed.hypograph IsClosed.hypograph
end Preorder
section PartialOrder
variable [TopologicalSpace α] [PartialOrder α] [t : OrderClosedTopology α]
-- see Note [lower instance priority]
instance (priority := 90) OrderClosedTopology.to_t2Space : T2Space α :=
t2_iff_isClosed_diagonal.2 <| by
simpa only [diagonal, le_antisymm_iff] using
t.isClosed_le'.inter (isClosed_le continuous_snd continuous_fst)
#align order_closed_topology.to_t2_space OrderClosedTopology.to_t2Space
end PartialOrder
section LinearOrder
variable [TopologicalSpace α] [LinearOrder α] [OrderClosedTopology α]
theorem isOpen_lt [TopologicalSpace β] {f g : β → α} (hf : Continuous f) (hg : Continuous g) :
IsOpen { b | f b < g b } := by
simpa only [lt_iff_not_le] using (isClosed_le hg hf).isOpen_compl
#align is_open_lt isOpen_lt
theorem isOpen_lt_prod : IsOpen { p : α × α | p.1 < p.2 } :=
isOpen_lt continuous_fst continuous_snd
#align is_open_lt_prod isOpen_lt_prod
variable {a b : α}
theorem isOpen_Iio : IsOpen (Iio a) :=
isOpen_lt continuous_id continuous_const
#align is_open_Iio isOpen_Iio
theorem isOpen_Ioi : IsOpen (Ioi a) :=
isOpen_lt continuous_const continuous_id
#align is_open_Ioi isOpen_Ioi
theorem isOpen_Ioo : IsOpen (Ioo a b) :=
IsOpen.inter isOpen_Ioi isOpen_Iio
#align is_open_Ioo isOpen_Ioo
@[simp]
theorem interior_Ioi : interior (Ioi a) = Ioi a :=
isOpen_Ioi.interior_eq
#align interior_Ioi interior_Ioi
@[simp]
theorem interior_Iio : interior (Iio a) = Iio a :=
isOpen_Iio.interior_eq
#align interior_Iio interior_Iio
@[simp]
theorem interior_Ioo : interior (Ioo a b) = Ioo a b :=
isOpen_Ioo.interior_eq
#align interior_Ioo interior_Ioo
theorem Ioo_subset_closure_interior : Ioo a b ⊆ closure (interior (Ioo a b)) := by
simp only [interior_Ioo, subset_closure]
#align Ioo_subset_closure_interior Ioo_subset_closure_interior
theorem Iio_mem_nhds {a b : α} (h : a < b) : Iio b ∈ 𝓝 a :=
IsOpen.mem_nhds isOpen_Iio h
#align Iio_mem_nhds Iio_mem_nhds
theorem Ioi_mem_nhds {a b : α} (h : a < b) : Ioi a ∈ 𝓝 b :=
IsOpen.mem_nhds isOpen_Ioi h
#align Ioi_mem_nhds Ioi_mem_nhds
theorem Iic_mem_nhds {a b : α} (h : a < b) : Iic b ∈ 𝓝 a :=
mem_of_superset (Iio_mem_nhds h) Iio_subset_Iic_self
#align Iic_mem_nhds Iic_mem_nhds
theorem Ici_mem_nhds {a b : α} (h : a < b) : Ici a ∈ 𝓝 b :=
mem_of_superset (Ioi_mem_nhds h) Ioi_subset_Ici_self
#align Ici_mem_nhds Ici_mem_nhds
theorem Ioo_mem_nhds {a b x : α} (ha : a < x) (hb : x < b) : Ioo a b ∈ 𝓝 x :=
IsOpen.mem_nhds isOpen_Ioo ⟨ha, hb⟩
#align Ioo_mem_nhds Ioo_mem_nhds
theorem Ioc_mem_nhds {a b x : α} (ha : a < x) (hb : x < b) : Ioc a b ∈ 𝓝 x :=
mem_of_superset (Ioo_mem_nhds ha hb) Ioo_subset_Ioc_self
#align Ioc_mem_nhds Ioc_mem_nhds
theorem Ico_mem_nhds {a b x : α} (ha : a < x) (hb : x < b) : Ico a b ∈ 𝓝 x :=
mem_of_superset (Ioo_mem_nhds ha hb) Ioo_subset_Ico_self
#align Ico_mem_nhds Ico_mem_nhds
theorem Icc_mem_nhds {a b x : α} (ha : a < x) (hb : x < b) : Icc a b ∈ 𝓝 x :=
mem_of_superset (Ioo_mem_nhds ha hb) Ioo_subset_Icc_self
#align Icc_mem_nhds Icc_mem_nhds
theorem eventually_lt_of_tendsto_lt {l : Filter γ} {f : γ → α} {u v : α} (hv : v < u)
(h : Filter.Tendsto f l (𝓝 v)) : ∀ᶠ a in l, f a < u :=
tendsto_nhds.1 h (· < u) isOpen_Iio hv
#align eventually_lt_of_tendsto_lt eventually_lt_of_tendsto_lt
theorem eventually_gt_of_tendsto_gt {l : Filter γ} {f : γ → α} {u v : α} (hv : u < v)
(h : Filter.Tendsto f l (𝓝 v)) : ∀ᶠ a in l, u < f a :=
tendsto_nhds.1 h (· > u) isOpen_Ioi hv
#align eventually_gt_of_tendsto_gt eventually_gt_of_tendsto_gt
theorem eventually_le_of_tendsto_lt {l : Filter γ} {f : γ → α} {u v : α} (hv : v < u)
(h : Tendsto f l (𝓝 v)) : ∀ᶠ a in l, f a ≤ u :=
(eventually_lt_of_tendsto_lt hv h).mono fun _ => le_of_lt
#align eventually_le_of_tendsto_lt eventually_le_of_tendsto_lt
theorem eventually_ge_of_tendsto_gt {l : Filter γ} {f : γ → α} {u v : α} (hv : u < v)
(h : Tendsto f l (𝓝 v)) : ∀ᶠ a in l, u ≤ f a :=
(eventually_gt_of_tendsto_gt hv h).mono fun _ => le_of_lt
#align eventually_ge_of_tendsto_gt eventually_ge_of_tendsto_gt
variable [TopologicalSpace γ]
/-!
### Neighborhoods to the left and to the right on an `OrderClosedTopology`
Limits to the left and to the right of real functions are defined in terms of neighborhoods to
the left and to the right, either open or closed, i.e., members of `𝓝[>] a` and
`𝓝[≥] a` on the right, and similarly on the left. Here we simply prove that all
right-neighborhoods of a point are equal, and we'll prove later other useful characterizations which
require the stronger hypothesis `OrderTopology α` -/
/-!
#### Right neighborhoods, point excluded
-/
theorem Ioo_mem_nhdsWithin_Ioi {a b c : α} (H : b ∈ Ico a c) : Ioo a c ∈ 𝓝[>] b :=
mem_nhdsWithin.2
⟨Iio c, isOpen_Iio, H.2, by | rw [inter_comm, Ioi_inter_Iio] | theorem Ioo_mem_nhdsWithin_Ioi {a b c : α} (H : b ∈ Ico a c) : Ioo a c ∈ 𝓝[>] b :=
mem_nhdsWithin.2
⟨Iio c, isOpen_Iio, H.2, by | Mathlib.Topology.Order.Basic.408_0.Npdof1X5b8sCkZ2 | theorem Ioo_mem_nhdsWithin_Ioi {a b c : α} (H : b ∈ Ico a c) : Ioo a c ∈ 𝓝[>] b | Mathlib_Topology_Order_Basic |
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